I know this sounds strange, but after many weeks of troubleshooting, I have pretty much come to the conclusion that if I keep my rutorrent page open in Firefox on my Centos install, it will eventually hang the whole pc.

Couple of months ago I have build a new 24/7 pc, to be my firewall/NAS and other sort of services provider at home.
This new build sometimes started to hang completely. Mouse did not move, could not connect to ssh, magic sysreq did not work.
Had to hard reset to get things working again.

What I have done:
- Checked and stress tested all hardware. No faults found.
- Used programs like monitorix and zabbix to monitor my resources like memory, swap, cpu etc. None seem to run into problems right before a freeze.
- Turned off all kinds of services/software. brought it back to bare minimum.
- kernel settings (noapic,pcie_aspm=off) and turning off offload settings on the NIC 'cause at one point I thought it was the NIC causing this

I did notice the freezes happened with different intervals. Sometimes twice a day, sometimes not for a month.

Because I always had my rutorrent screen open in firefox when a freeze happened, I started to see if this had something to do with it.

For a month, I made sure to not leave that screen open or in the the front (just some random other tab). For the whole month no freeze.
Just a minute ago, I accidently left it open on rutorrent for I think 30 mins, and got another freeze/hang.

I am completely baffled by this and would like to ask you guys for some suggstions how to further troubleshoot this as I really want to get to the bottom of this problem.

Some additional info:
Centos 6.5, updated recently.
desktop is XFCE
Current firefox version is firefox-31.1.0-5.el6.centos.x86_64, but it happened with previous versions.

Let me know if you need more info on something particular.

I'm not a linux newbie, so should be able to understand complicated steps if necessary.

Thanks for thinking with me on this!