[Typo3] Session timed-out Error

[Simon Angling]

I seem to be getting the following error a lot:

Login-error or session timed-out
No user logged in! Sorry, I can't proceed then!
(You must have cookies enabled!)
If your session has just timed-out, you may
click here to re-login.

I'm getting this error both on my Windows and Linux boxes at home - from the
office though everything seems fine. Sometimes from home I can't get in at
all as this error appears on logon - sometimes I can make a few clicks in
the BE before I get this.

I've checked my cookie settings, etc - even turned of the firewall (just in
case) - but can't seem to work this out.

Any ideas anyone.

Cheers,
Simon