The link that hoppy785 was talking about:
It's a well documented bug (Intel) in the kernel. (Jaunty, Gloria, & all other distros that use the same kernel)
It is a little more difficult, and has to do with upgrading your kernel , so read the whole post, and use at your own discretion / risk.
I followed Katzedecimal's instructions, and my Intel 945 system is working perfectly. ( and fast )
Edit: You might also benefit from trying the fix listed here: http://ubuntuforums.org/showthread.php? ... hlight=awn