Display driver crashing-radeon HD 5470  

I have ACER Aspire 5741G with Radeon HD 5470 and i5 processor,win7 x64.
Display driver sometimes simply stops working during videoplayback in mediaplayers or streaming videos on youtube,everything stops working,black screen comes up and then starts driver video recovery. Notebook is new and I have installed the latest driver,even tryed removing it completely and installing it again but nothing seems to be working:-(

Its a TDR error
Causes: bad RAM, incorrect RAM timings/voltages, bad GPU, overheating

Test your RAM: RAM - Test with Memtest86+

Test your graphics card in another PC

Thanks,but I can't test my graphic card since this is laptop (brand new) that we are talking about:-(
Hm,maybe overheating is the problem?!
I saw one guy had the exact same problem with the same laptop,who also couldn't find the solution.