Here's a curly one... I can't share calendars in Outlook/Exchange. When you are in Outlook (any version), going to Tools | Options | Calendar Options | Resource Scheduling, I get a "The operation failed" dialogue with no further information.
Nothing in the event logs on the client or the server, the mailbox has been shared out and given maximum permissions, I am logged in either as myself (I am a domain admin), or the domain admin a/c, or made a test mailbox and logged in with those credentials, but any mailbox here gives the same error. Exchange is 6.5 SP2 on a 2k3 SP2 box and is a domain controller.
I've done a long hard creative trawl through google, but drawn a blank. Any takers?