Portguese keyboard is partial incorrect

What version of Ubuntu are you using? This can be found using 'lsb_release -rd' from the command line.
Which windowing system are you using?
The precise method used to set the keyboard layout depends on which Ubuntu you are using and how you are using it.

Ubuntu 11.10 comes with fourteen (14) distinct Portuguese layouts (admittedly, some of these are probably not used by anyone). The solution to your problem is probably to make the correct choice from among the 14.

Portuguese
Portuguese (Brazil)
Portuguese (Brazil, Dvorak)
Portuguese (Brazil, eliminate dead keys)
Portuguese (Brazil, nativo)
Portuguese (Brazil, nativo for USA keyboards)
Portuguese (eliminate dead keys)
Portuguese (Macintosh)
Portuguese (Macintosh, Sun dead keys)
Portuguese (Nativo)
Portuguese (Nativo for USA keyboards)
Portuguese (Sun dead keys)

I updated the question with the version of Ubuntu, sorry about that.

Thank you for the help, although, I'm not saying I don't know which version to choose. I'm saying that the "Portuguese" layout (1st in the list) the one I usually choose and the layout of most Portuguese European Keyboard is not correct in this version of Ubuntu (and it was before). I also tried to used the different layouts without success.

Check if you are gettinjg third or fourth register (Alt and Shift-Alt) characters. Check if you are able to type characters that require dead key combinations.

AltR is the right Alt key. Denote the key that is two keys to the right of the l key by (L+2). Record the results of these experiments:

(1) Type the A key (lower case)
(2) Type Shift-A
(3) Type AltR-A (a character in third register)
(4) Type Shift-AltR-A (a character in fourth register)
(5) Type Alt-(L+2). Then type A (this is a dead key combination and should place a caret above an 'a')

aAæÆâ

Jacobsallan, the problem is:
This is the Portuguese Keyboard layout: http://en.wikipedia.org/wiki/File:KB_Portuguese.svg

And in 12.04 the keys for [çÇ] [\|] [~^] [ºª] [+*] and [«»] are not in the correct position.
 If you use the system setting's keyboard app, select Portuguese and see the preview you will see the difference from the layout in wikipedia link (which is correct).

Thanks for the help

I meand 11.10 rather than 12.04, sorry about that

Please report the languages listed in System Settings->Keyboard Layout. Start up the "System Settings" application. Double click the "Keyboard Layout" icon. Choose the Layouts tab. The mappings are in the textarea on the left.

The map at http://en.wikipedia.org/wiki/File:KB_Portuguese.svg is incomplete. Ubuntu 11.10 ships with a more complete description of the Portuguese Linux keyboard mapping. We are going to see how your computer matches up this mapping.

Start up the "System Settings" application. Double click the "Keyboard Layout" icon. Choose the Layouts tab. Select Portuguese, if there is more than one mapping on your machine. To the lower left there are icons one of which looks like a keyboard: click it.

Start typing into a terminal. Copy and paste the results here. You will need to exercise some care with dead keys.

Register 2 has Shift key on, register 3 has RAlt on, and register 4 applies Shift+RAlt. My computer types the following:

Row 1, register 1: \1234567890'«
Row 1, register 2: |!"#$%&/()=?»
Row 1, register 3: ¬¹@£§½¬{[]}ç (type a lower case 'c' after the dead key at the end of the top row)
Row 1, register 4: ¬¡⅛£$⅜⅝⅞™±°¿ǫ (type a lower case 'o' after the dead key at the end of the top row)
Row 2, register 1: qwertyuiop+ó (type a lower case 'o' after the dead key at the end of the second row)
Row 2, register 2: QWERTYUIOP*ò (type a lower case 'o' after the dead key at the end of the second row
Row 2, register 3: @ł€¶ŧ←↓→øþäñ (type a lower case 'a' and lower case 'n' after the two dead keys at the end of row 2)
Row 2, register 4: ΩŁ¢®Ŧ¥↑ıØÞåā (type lower case 'a's to capture the two dead keys at the end of the 2nd row)
Row 3, register 1: asdfghjklçºñ (type a lower case 'n' to capture the dead key at the end of row 3)
Row 3, register 2: ASDFGHJKLǪâ (type a lower case 'a' to capture the dead key at the end of row 3)
Row 3, register 3: æßðđŋħjĸłóôǹ (two lower case 'o's and a lower case 'n' capturing the 3 dead keys at the end of row 3)
Row 3, register 4: ƧЪŊĦJ&Łőǒŏ (use three lower case 'o's to capture the 3 dead keys at the end of row 3)
Row 4, register 1: <zxcvbnm,.-
Row 4, register 2: >ZXCVBNM;:_
Row 4, register 3: |«»¢“”nµ·ạ (type an 'a' to capture the final dead key. skip the key to the right of µ )
Row 4, register 4: |<>©‘’Nº×÷ȧ (type an 'a' to capture the final dead key)

My current keyboard is a Windows 104-key keyboard ( http://en.wikipedia.org/wiki/IBM_PC_keyboard ), so I can only make a good-faith effort at replicating your problem. In particular, my keyboard has a z immediately to the right of the left Shift key and yours probably has a <-key. You may have a bug specific to a Windows 105-key keyboard. But, I don't think this is the case. I did a massive amount of keyboard testing of Firefox on Ubuntu with a proper 105-key keyboard and never observed a discrepancy of the kind you described in any of the Linux keyboard layouts.

The keyboard I'm using its "Portuguese" and if you see the mappings (using the review button) you will see is not the correct layout for a "Portuguese" layout (in all previous versions of Ubuntu it was correct). The wikipedia link I posted is note complete as it doesn't show all combination keys possible, but I don't believe that the problem is with the combinations but the position of the key itself. If you compare the two layouts they are different and they are different in the keys I mention in my reply 4 (I only mentioned the modification using shift, register 2 in your request).

I will post the output in my next reply since I'm not using Ubuntu 11.10 in this computer.

Thank you again for your help.

I'm sorry for the late reply, but in the last update I've done, the problem was fixed and the "Portuguese" keyboard layout is now under "Portuguese (Nativo)"
Thank you for relplying and for all the help provided.

Well it seemed to be too soon to talk. I was playing around with the different layouts and when I choosed again Portuguese (Nativo) or Portuguese I had the same error again the keys being switched and now a message box apears with the following error:

Error activating XKB configuration.
There can be various reasons for that.

If you report this situation as a bug, include the results of
 • xprop -root | grep XKB
 • gsettings get org.gnome.libgnomekbd.keyboard model
 • gsettings get org.gnome.libgnomekbd.keyboard layouts
 • gsettings get org.gnome.libgnomekbd.keyboard options

This is a computer. If it is functioning properly, the keyboard should behave the same when run with the same software. If you are using a desktop get another keyboard and try using it. This may be a hardware problem.

Jacobsallan: It is a laptop and I tried with external keyboards and none worked properly. I've seen this issue reported by other Portuguese users.