Ubuntu :: Kernel Panics In Natty All The Time?

I have been a happy Ubuntu and other distros user from 2007 to now. Had my old 7.10 Gutsy Gibbon (Ubuntu Studio actually) that I really felt was time to upgrade. Then I downloaded the ISO image for 11.04 Natty Narwhal past 4 day ago. It gave me an option to install on my old 7.10, upgrading it, then I chose that one not to have to lose my data.

At the very end of the installation (when downloading several packages from the net) I got a kernel panic.
After that I reinstalled from zero wiping the whole partition, with the same results. It only worked when I disconnected the net cable so it wouldn't download anything during install. Then I could run the 11.04, but kept getting kernel panics, and after some testings (I thought it was the nvidia video drivers at first) I think it happens after some ammount of network traffic happens.

Memtest went normal, I tried logging with no-effects and I tried some solutions from forums with no results. The pc can be on and working for hours, but after I start surfing the web for some time, I get a freeze. Sometimes Caps Lock and Scroll Lock leds are flashing, and sometimes just freezes to simply become unresponsive. When it was during the installation I got a message saying it would pop out into console because panic occured and then froze. Anyway I always have to press the reset button.

I would like to be sure if I have some of my hardware broken or if the newest kernel is still green on some hardware support; maybe network. I'd also like to know if I can install older versions of the kernel; I think that should fix the problem because other distros worked perfectly here before. I also heard about some kernel-image-pae being different from the ordinary kernel image. Could it help if I change that package? I'm waiting to install 11.04 in my wife's computer also but of course I don't want to bring any problems on her! My net card is Nvidia Nforce and my processor is AMD Athlon II X2 with a GForce 9400 for video card.