Outlook 2010 sporadic shows the wrong mailbox quota (Exchange Server)

Hello,

in our Exchange environment with Win7/Office2010 clients, some users have sporadic the following problem:

Outlook suddenly shows a warning in the upper status bar, that the mailbox quota has been exceeded.

I we look into the Account Information tab, it shows a maximum mailbox size of 50 or 200MB. But all users have 2000MB mailboxes. We checked the mailbox on the Exchange server, but there all settings are correct (2000MB).

In most cases the message disappears automatically after some minutes and then Outlook shows the correct size of 2000MB.

When the problem last time occured we let the user login to his OWA page -> it showed the correct size.

So it seems a local problem with Outlook.

Does anyone have a clue, what could be the cause?

Thanks,