AD connecting to Exchange

I have 2 servers, 1 is the windows2000 DC that houses the AD and 2 is the windows2000 server that has Exchange2000.
On the DC, (before SP3) I was able to go to Users and Computers and edit a USER's email account information to add an aditional SMTP email account (like an alias) I now get the following error.

Microsoft Active Directory - Exchange Extension

facility: Win32
ID no: c00706b6
Microsoft Active Directory - Exchange Extension

Under the Exchange Advance, I was able to modify the rights, but now I get the following:

Microsoft Active Directory - Exchange Extension

The action could not be completed because the Microsoft Exchange Information Store service is unavaible. Be sure the service is running and you have network connectivity to the Microsoft Exchange Server computer

ID no: c1041721

I can only cancel out of this command. Before SP3 I was able to do this. When I create a new user it will create the mailbox on the exchange server.

Any idea?