Two minutes is a very short time. I've not had a similar experience for a long time but when I did lose sessions I seem to remember the issue I have was related to an AntiVirus plug-in wiping my cookies and the other was when I was trying to use a WiFi hot-spot which was configured to provide additional security by continually cycling network address.
The AV problem was solved by telling it to leave ebay cookies alone, the Wifi thing went in the bin.
As with all debugging, try to simplify things as much as possible - switch off addins and the like, then keep an eye on the console for errors/warnings for any clues.
