I applied the update a while ago to office that causes the 'Office Live Workspace' dialog to show at start-up but the tick box to stop dialog from showing every time has never worked and tonight has been the  first night I've needed to use Office in a while so I thought I see if I could fix this annoyance. 

After a quick search it turns out the problem is the installer for the update only sets up the registry for the current user and as I always set up an admin account separate form my day to day user account my registry didn't have the necessary keys and thus the dialog would  always appear. There is another update that solves this problem and it can be downloaded from Microsoft. There is a Aaron Rykhus has a TechNet blog post that explains everything in more detail if you want to check it out.