Upgrading to 7 shudn't be the problem...
My laptop came with Vista but I upgraded to Win 7 last year in August. There weren't any problems then. This issue came only last thursday. Then only I went in for re-installation of Win 7. Its a bit unorthodox to say this, but this problem just came outta the blue! And I'm not able to pin down the actual source of the prob.
Although I tried installing K-lite full (made no difference) earlier, I've tried shark 007 now.... No noticeable improvement