Outlook 2003 Exchange 5.5

[Peter]

I have a new install of Exchange 5.5 on a win 2k server.
All mailboxes move without any problems and access is fine
using Outlook 2003 for most.

There are 2 mailboxes that cannot be accessed using
outlook 2003 but will work fine with outlook 2000. Has
anyone had this problem before or know of a
cause/solution.

Thanks in advanced
Peter