Black Screen while playing games

I searched a lot for this problem and found this forum via google.Lots of people are having same problem here also.I have detail explanation of my problem below,plz be atient.Hope you guys can help me :)

Now,here is my problem.It started about 2 weeks ago i think but not sure.When i was plating MAfia 2,screen went black and the monitor's power signal was going on/off.Nothing worked so i have to restart my computer with restart button.No bluescreen message nothing just black screen.Then it started happening in other game like PES 2010.But the black screen appears only when the 3d is rendered i think cause the game menus works fine.As soon as the game is started,the blackscreen appears randomly.sometime i can play for 1/2 hr,sometime immediately after starting the game.
So i reinstalled new driver(latest),used driver sweeper,cleaned my cpu case,blew some dusts,removed gpu card(msi 9800gt) and placed it again.

After doing all this it worked until 1 week i think.All was going well till 2 days ago it started happening again.This time all my games crashed immediately after starting them(no crash in menu screen).I checked GPU team in gpu-z and msi afterburner and they are fine.(idel 55 C, on load 78 C).so i again reinstalled nvidia driver,removed my cpu case and just unpulgged and re plugged my HDD cable,fans power cables and now the games working fine.

But i was curious what it causing the problem and googled a whole thing and found out about driver issue,MB issue,bios issue,driver issue,PSU etc in various forums.I also came to know about verifier.exe in win7 last night and the dump files.i tried to check dump files but due to some problem it doesn't show correct data.On one file i found something like dxgkrnl.sys and nvlddmkm.sys.I then ran verifier.exe to check these two driver and it restarted nornmally without any bluescreen.However everytime i started verifier.exe to check all the driver it showed BSOD after windows started.

So please guys help me to find out what's causing the problem.Is it hardware issue or some driver?I have explained lots of things and attached the dump files.Hope this will help

My Spec:
CPU C2D E7200 2.53GHZ
GPU: MSI 9800GT 512MB OC(factory overclocked,i haven't changed anything)
PSU: local brand goldkist 550W
MB: msi g31
RAM: muskin 2GB 800mhz
HDD: 2 HDD,160GB(OS) and 320GB
OS: Win 7 ultimate

This is caused by nvlddmkm.sys, part of the Nvidia drivers

Causes:
Bad memory/PSU/PCI slot/GPU/bad driver/incorrect RAM timings or voltages

Test your memory with memtest86: RAM - Test with Memtest86+

Remove Nvidia drivers by using Driver sweeper: http://www.guru3d.com/category/driversweeper/
Then reinstall the current drivers in safe mode

Test the 9800GT in another PC if possible

This was likely caused by the following module: nvlddmkm.sys
Bugcheck code: 0x117 (0x85289510, 0x908EE326, 0x0, 0x0)
Error: VIDEO_TDR_TIMEOUT_DETECTED
Dump file: C:\Windows\Minidump\100210-27562-01.dmp
file path: C:\Windows\system32\drivers\nvlddmkm.sys
product: NVIDIA Windows Kernel Mode Driver, Version 258.96
company: NVIDIA Corporation
description: NVIDIA Windows Kernel Mode Driver, Version 258.96

Thankx 4 the quick reply.I have used driver sweeper to clean the driver.however i reinstalled driver in normal windows mode not in safe mode.Have you seen the latest 4 dump files?I used "bluescreenview" and it showed "RTCore32.sys" as red flag.Those latest dump files are created while running verifier.exe.Can this "RTCore32.sys" be the problem?I thinks it's driver for rivertuner or afterburner.I have both installed.

I will do the memtest when i get home.Thanks again for quick reply

Hai people sorry for the late reply.I don't know why but "RTcore32.sys" always gives BSOD while using verifier.exe.I think my problem is due to dust on card or card not placed firmly on pcie slot.

i installed new game pes 2011 and tried to play it,but same problem occured.So i restarted my computer and tried to play other games.All games crashed.Then i went in safe mode,tried to do some stuffs,this time black screen appeared when i was in desktop in safe mode.i tried to restart but the black screen didn't went this time.I restarted 2/3 times and the screen showed message saying "you have changed some hardware" etc.so i took my GPU and plugged LCD cable to default motherboard vga and it started without any issue.

So i took my GPU fan/heatsink and cleaned all dusts and put it back on pcie and restarted my comp.It's working fine till today without single crash.

can dust get these problem?i am very confused.Hope this problem won't happen again.Also i haven't applied any thermal paste again in my gpu after i removed it.The GPU seems to increase by 2/3 number.Is it ok if i don't apply new thermal paste and use as it is for now?

Thank u guys for the help.Really appreciated for your valuable times.