BSOD, Ethernet disconnects, clock changes

First off, thanks so much for any advice you guys might be able to give me. This is a great forum, just never had to sign up until now. If my question needs to be relocated to another section of the forum, please let me know : )

My issue is that I've recently been getting frequent disconnects from my wired Ethernet connection. This is usually sporadic and doesn't seem to have causal origin. I can usually last about 1-2hrs before it disconnects and less if I happen to be streaming video over my network (using my computer as a server w/ tversity or another streaming app to the xbox or another computer etc). When this happens, I only have to re-enable the adapter to connect back to the internet. However, when I re-connect, my clock rolls back to an earlier time, about 1-2hrs- causing me to re-sync with windows time server.

In my attempt to remedy this, I've changed the power management property of the adapter, un-checking the "Allow the computer to turn off this device to save power" option. I've uninstalled the adapter and re-installed with the latest realtek drivers. I even bought a new Intel Pro/1000 GT Adapter and disabled the onboard ethernet adapter. Then, I set the intel adapter with the same power management option un-ticked. None of this has helped.

Other symptoms are as follows:
Every one to two days I'll get a random BSOD in which nothing appears but "Memory Parity Error".
Sometimes the computer will just halt in a deep freeze, where audio will continue in a loop until the system is shut off. These deep freezes don't follow any specific behavior other than using multiple programs at the same time.

I don't know if perhaps this might be a virus issue. I have Avast installed and did multiple passes with no results. I noticed someone on this forum that kind of had a similar problem, as I've described regarding the disconnections, and was remedied by applying a few fixes with hijackthis.

Here are my system specs:
Windows 7 64bit
i5 2500K (not overclocked)
ASRock Z77 Pro4 Motherboard
EVGA GeForce GTX560 Ti (01G-P3-1561-AR)
16GB (4*4GB) G.Skill Kit (F3-12800CL9Q-16GBXL)
3 * Samsung 1TB HDD (HD103SJ)
Corsair CMPSU-750TX 750W PSU

Any help would seriously be appreciated!
 
Thanks for the response. I'm doing everything you recommended right now. Strange that such issues could possibly come about from Avast... but I guess I'm about to find out!
 
Cool, so uninstalling Avast was definitely the right call (also used ccleaner to clear out the registry, temp files etc). Shorty after, I got another 2 deep freezes that required a reset. So, I got down and dirty- blowing dust out of every nook and cranny I could find, re-seated my cpu w/ new thermal grease, uninstalled my graphics card driver completely and then re-installed it and finally replaced my cmos battery.

Everything is now good as new. My clock no longer rolls back, no Ethernet disconnects, no freezes and my system runs a lot faster. Microsoft essentials seems to be the ideal antivirus solution... kinda surprised by that one. You really don't even notice it's there. Thanks again.
 
I use avast! on a number of XP systems with no problems. With all the other things that user did after uninstalling avast!, how can we be certain that was the cause?
 
Avast runs fine on most computers, and XP. With Windows 7, it's firewall and the other included defense programs get corrupted by 3rd party antivirus programs sometimes. This is one of those times
 
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