Thanks all. Have already checked start up apps and services, but I'll give it another shot. Uninstalling IE9 hasn't stopped the slow log off, but the time taken has reduced to about 5 mins. Interestingly, noticed that the screen briefly flickers before any freezes occur. After a few minutes IE everything starts working again, so it looks like an app is crashing in the background which later on causes difficulties logging off. Two more Windows updates last night, maybe they will help? I am somewhat doubtful, but here's hoping.