Ubuntu freezing problems (6.06 & 7.04)

I have searched to find people with problems like mine. Many are similar, but they all have something in common that I don't: It actually loads for them, then freezes.

I'll start off by saying I have 2 computers I'm putting Ubuntu on. One runs it just fine. Ubuntu 7.04 The other one is giving me the problems. Here are some specs

ComputerA (The one that works)
- Athlon XP 1900+
- 1gb DDR
- ECS N2U-400 motherboard using onboard ethernet and sound
- 32MB GeForce 2 MX 440
- 40 & 200 GB ATA hard drives

ComputerB (My preferred computer that's giving me trouble)
- Athlon64 3000+ (Socket 754 version)
- 2 GB DDR
- Chaintech VNF3-250 motherboard using onboard ethernet
- 128 MB ATI Radeon 9800 Pro
- CL SoundBlaster Live! 5.1
- 160 GB SATA hard drive

ComputerA installed from the LiveCD first time with no problem at all and has been running for about a week. ComputerB has taken 3 days of my time and counting.

I first tried Kubuntu 7.04 on this one since my other was running Ubuntu. I downloaded the 32bit livecd iso and burned it. Put it in, booted up, ran a disc check, continued on to run the livecd. It froze at different times. Sometimes with the splash up, sometimes on a black screen after that and before loading, and during the graphical loading (when it says loading nautilus, etc) Never once made it all the way in. I decided to just use the Ubuntu disc I used on the other computer. Nope. Same issue.

I read around on forums and such and found people saying they had similar problems then added some "irqpoll acpi=off ..." commands (4 in all, don't recall them right off - actually found them on this site) and that solved their problems. Didn't solve mine. I also saw some people mention using the alternate cd and the text install worked for them. It did for me as well, until I actually tried booting into it. I would have the same problems. It installed great, but would freeze at the same times as before. I then tried the same commands I mentioned above in the /kernel line as well as removing "quiet splash" so I could see if there were errors but there weren't. It would freeze after all the text is gone and the screen is blank. I did manage to see the login screen a couple times and logged in, but it would freeze before I could do anything. It's nearly instantaneous. Click login and freeze. Also, I can boot into text mode with no issue.

I'm about to try a 64 bit version but have continued with the 32 bit because the Ubuntu site says "if you need full support for 32-bit code, use the Intel x86 images instead." I wasn't sure if 64 bit would cause me problems in the future or not so decided to play it safe with the 32 bit version as the site suggested. I'm currently downloading the 64 bit version (at over 1MB/sec so it will be done soon, gotta love torrents) and will be trying that shortly. I'll post back with results.

This seems to be a common problem. I see all of these posts mentioning some "fixes" everywhere that either don't work or require me to go into the system menu (the powernowd thing - which I have never seen because it freezes before the bars load). Is there a definitive answer to why this is such a big problem right now?

Thanks everyone.

Also, I should note that ComputerB (the one I'm having problems with) has WinXP installed and has had no problem for over 2 years installed time and has excellent cooling. Even the graphics card has an aftermarket cooler on it.