Log on problems
 

I logged on earlier and there were no problems. I came to log on again about 1hr later and was greeted with the "you are a guest" etc page.

Is there any particular reason why this should have transpired please given that I do not log out and have never encountered this previously ?.

Have you, or anyone, made any changes to the browser, run any cleanup program, or installed/run any other software in that time?
Seems likely a cookie was deleted or expired.