using 11.04 can only use safe mode or classic

What is your architecture? Unity 3D only runs if you have a 3D graphics card. If not then you can run Unity 2D. Is this the case?

[If you understand Jason's explanation of a possible cause for this problem, and are able to use that to fix the problem and/or provide the information that Jason as requested, then please do so. Otherwise, please read on... (I composed this reply before Jason submitted his--Jason's reply may fix your problem quickly, but my reply is more geared toward novices.)]

Log in with an Ubuntu Classic session and run System > Administration > Additional Drivers. This will show you if there are any video card drivers available for your computer. Installing such drivers might fix this problem. If there are no drivers available, or there are but installing them doesn't solve the problem (be sure to reboot first, to make sure), then please open a Terminal window (Ctrl+Alt+T or Applications > Accessories > Terminal) and run this command:

sudo lshw -c video

I recommend copying and pasting that command, rather than typing it manually, as the former is easier and reduces the chance of typos. After pasting or typing it in, press enter to run it. You may be prompted for your password. As you enter it, you won't see any placeholder characters (like *). But that's OK--just type it in and press enter.

Then, when the command finishes, please select all the text from the Terminal (Edit > Select All), copy it to the clipboard (Edit > Copy), and paste it here for examination. Please also describe in detail what (if any) options there were for drivers to install (back when you went into Additional Drivers).

i have an nvidia GeForce FX 5200. i ran additional drivers and it says that the nvidia accelerated graphics driver (version 173) is activated but not in use

 *-display
       description: VGA compatible controller
       product: NV34 [GeForce FX 5200]
       vendor: nVidia Corporation
       physical id: 0
       bus info: pci@0000:01:00.0
       version: a1
       width: 32 bits
       clock: 66MHz
       capabilities: pm agp agp-3.0 vga_controller bus_master cap_list rom
       configuration: driver=nvidia latency=248 maxlatency=1 mingnt=5
       resources: irq:18 memory:fc000000-fcffffff memory:f0000000-f7ffffff

Same situation as Ryan, with these results from lshw--

*-display
       description: VGA compatible controller
       product: G72 [GeForce 7300 LE]
       vendor: nVidia Corporation
       physical id: 0
       bus info: pci@0000:02:00.0
       version: a1
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress vga_controller bus_master cap_list rom
       configuration: driver=nvidia latency=0
       resources: irq:24 memory:fa000000-faffffff memory:d0000000-dfffffff memory:f9000000-f9ffffff memory:fbde0000-fbdfffff

Pretty much the same problem, my results are:

  *-display
       description: VGA compatible controller
       product: G71 [GeForce 7300 GS]
       vendor: nVidia Corporation
       physical id: 0
       bus info: pci@0000:01:00.0
       version: a1
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress vga_controller bus_master cap_list rom
       configuration: driver=nvidia latency=0
       resources: irq:18 memory:d0000000-d0ffffff memory:c0000000-cfffffff memory:d1000000-d1ffffff memory:d2000000-d201ffff

I have same problem:

description: VGA compatible controller
       product: 82865G Integrated Graphics Controller
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 02
       width: 32 bits
       clock: 33MHz
       capabilities: pm vga_controller bus_master cap_list rom
       configuration: driver=i915 latency=0
       resources: irq:16 memory:f0000000-f7ffffff memory:fc400000-fc47ffff iopor