Most common I run into is an expired antivirus suite. Really weird effects just like you listed.
Bob
Hi everyone,
I'm having a lot of trouble finding out what's wrong with my dad's pc. He's running Vista 32-bit on an HP Pavilion desktop with an Atheros network adapter. Windows says wi-fi is fine, but recently Google Chrome stopped working. A few days later, Firefox and IE and all other internet services stopped as well.
I tried to figure out if it was a hardware or a software problem, so I tried a USB network adapter, didn't work either. Today our new fibreglass connected router was installed and the problem persists.
So I'm thinking this is a software problem, do you have any idea?
Thanks,
Joep

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic