P-7805u monitor turns turns off on AC power only...

So I just bought a 7805u FX off ebay- refurbished.
When I have the AC adapter plugged in, the monitor will shut off during anything that uses the gpu- and sometimes just randomly. It will even shut off during games like chess and solitaire. The computer stays running, but the only way to get it back on is to hard reset it.

I just found out, however, when its running on just battery everything works fine- even with games like COD5.

I called and got an RMA. But before I spend the $30+ to ship, and two weeks wait time- I thought I would see if anyone on here has any suggestions.
Could it just be the power supply? If so, I could just get one off ebay for cheaper than me shipping the laptop, and quicker than waiting.

There is no dust anywhere, and I checked the temps- its running cool.
Plugged in, I could start windows up- turn a game on right away, and the monitor would shut off- so im 100% positive its not a heat issue.

Thanks for your suggestions!!

 

Sorry...I have windows 7. And I've done every driver upgrade, and I deleted windows 7 and reinstalled...and tried upgrading drivers from the definitive driver upgrade method.
I can't imagine it's a driver problem since it works fine on battery power.
Normally, laptops dont work on battery power!

 

No suggestions??

I figured this was a little more difficult than most other problems. I'll just send it in tomorrow

 

Is there another AC adapter you can try? Or can you try the adapter on a separate but same similiar requirement laptop?

 

No, I would have to buy one- and try that way. I still havent sent it in. Im gonna send it in tomorrow though