Hi there,
Please let me know if there is another forum somewhere that can provide me with more technical help

I have ubuntu 12.04 installed on a Intel® Core™2 CPU 6600 @ 2.40GHz × 2
There is 3GB of memory, 250GB disk. Video Nvidia 265mb
This computer used to be a Windows 7 and Windows XP, but now runs Ubuntu 12.04 LTS.
aperture@aperture:~$ uname -a
Linux aperture 3.2.0-23-generic-pae #36-Ubuntu SMP Tue Apr 10 22:19:09 UTC 2012 i686 i686 i386 GNU/Linux
The Problem:
Basically ever since I installed ubuntu 12.04, this thing freezes randomly. This freezing is COMPLETELY random, and is MORE FREQUENT when used. Highest frequency is when I am downloading something, but freezes at any time (not used - but we run apache, playing videos, youtube, etc..). When freezes the mouse and keyboard do not respond, it's not just graphics, but the entire thing. If it's playing sound, it loops the last 1/2 second of it over and over until we reboot it or it resets by itself (~5seconds). Works perfectly after reset, but sometimes the graphics gives error or resolution messed up (hence we thought it was video card).

What I tried:
1. Installing 11.04 - same problem
2. Reformatting the HD (before had windows partition), and re-installing ubuntu 12.04 - same problem (problem out-of-box even before updates/software)
3. SD RAM Check - no errors
4. File system check - no errors
5. Replaced RAM - same problem
6. Replaced video card - same problem
7. Re-installing windows - WORKS

Other info
DMESG right after reboot: http://pastebin.com/V0tmM8nh
I'm not an expert but haven't noticed anything significant, maybe you guys can take a look.
syslog a min after reboot; http://pastebin.com/D6nZhFX4

Please let me know, I will provide any other info necessary.
Please help me figure this out. I love ubuntu, and I'd hate to switch back to windows.
If you guys have any idea about other places I can post this, please let me know.

Thanks so much.