You are possibly using cached mode against Exchange 2003.
You really need to contact your administrator about this issue. I think it
might be fixed by one of the updates.
Cached mode can be turned of by:
To enable or disable Cached Exchange Mode, follow these directions:
1.. In Outlook, from the Tools menu, select Email Accounts... .
2.. In the window that opens, under "Email", make sure the radio button
next to View or change existing email accounts is selected, then click Next.
3.. Highlight your Exchange server account, then click Change... .
4.. To turn on Cached Exchange Mode, under "Microsoft Exchange Server:",
check the box next to Cached Exchange Mode. To turn it off, remove the
checkmark from the box. Click Next, and in the window that opens, click OK.
5.. Click Finish. You must restart Outlook for the change to take effect.