mcfly, guino's probably right cos as you mentoned it keeps logging you out, it's ending your session even though you've logged in. Maybe deleting your cookies. I too doubt it would have anything to do with router or company firewall settings. Although you may still be right when saying that the problem is with the "workplace PCs", probably with the local PCs themselves, or the way your IT department may have set them up, domain security, etc.

