Firefox closes, internet doesn't work all of a sudden!?

[Srk]

I have Windows XP service pack 2. For the last 2-3 days, once in a day:
Firefox closes on it own, Chrome remains open but no site opens while the net connection is on. I restart Firefox but that too can't open any site.
every time this happened, I was not doing anything, didn't open any site/link.

Once I got this error in the 'event viewer':
The System Restore filter encountered the unexpected error '0xC000009A' while processing the file 'etilqs_fh1iLGKv5Yu4Du8' on the volume 'HarddiskVolume1'. It has stopped monitoring the volume.

But today no error appeared. Can someone please help me deduce what's going on?

[Bobby]

Your PC is infected with some kind of virus.Its better to do a system scan and disinfect your pc or you can try reinstalling your web browsers.