I'm also probably going to bed soon (having been up all night), so I'll keep my reply brief.
I'm using Firefox 12, and I've got used to hitting F5 immediately after posting on AB, to get round the caching problem. (it doesn't really bother me that much).
Try turning off automatic updates (in FF11) to see if it helps you. Go to Tools > Options > Advanced > Update(tab) and select 'Never check for updates'.
Thanks Chris for your response........I had already tried turning off 'updates' which also had been suggested by Aquariel in my earlier thread. However, the problem persisted until I tried another course of action.
Went into 'programmes' and removed FF 11 and then re-installed from original downloaded file. Have also re- ticked the box 'Never check for updates'...Fingers crossed that the problem doesn't return.