Has anyone successfully converted their mailboxes from Exchange 5.5 running on Windows NT 4 to Zimbra network edition?

Here's our environment:

Windows 2000, single Active Directory domain
Exchange 5.5 on a Windows NT 4 member server
Active Directory Connector not installed

When I use the v.4.0.0 ZCS migration wizard, it converts a few items, but I always get errors and it never finishes.

Here is the last few lines of one log file:

31-10-2006 08:28:13 [2604]: (MI): Batch Added Message rid(4)
31-10-2006 08:28:13 [2604]: (MI): Executing batch request
31-10-2006 08:28:15 [2604]: (MI): Got response (1968 ms)
31-10-2006 08:28:15 [2604]: (MI): Batch Adding Contact d(No Date) fid(007) c((null) (null))
31-10-2006 08:28:15 [2604]: (MI): Batch Added Contact rid(0)
31-10-2006 08:28:15 [2604]: (MI): Batch Adding Contact d(Wed, 7 Apr 1999 19:35:02 -0000) fid(007) c(John Smith)
31-10-2006 08:28:15 [2604]: (MI): Batch Added Contact rid(1)
31-10-2006 08:28:15 [2604]: (MI): Adding Appoinment d(Tue, 13 Apr 1999 15:47:02 -0000) fid(010)
31-10-2006 08:28:15 [2604]: Clearing internal progress log entries
31-10-2006 08:28:15 [2604]: Entries cleared
31-10-2006 08:28:15 [2604]: Error while importing mailbox jsmith@somedomain.org: OOM Exception Unable to Process Appointment (null)
31-10-2006 08:28:15 [2604]: Waiting for work
31-10-2006 08:28:15 [2604]: Worker thread exiting


Here is another example of a different error:

11-10-2006 16:16:17 [340]: (MI): Batch Added Message rid(29)
11-10-2006 16:16:17 [340]: (MI): Executing batch request
11-10-2006 16:16:18 [340]: (MI): Got response (875 ms)
11-10-2006 16:16:18 [340]: (MI): Batch Adding Message d(Wed, 11 Oct 2006 19:40:48 -0000) fid(005)
11-10-2006 16:16:18 [340]: (MI): Batch Added Message rid(0)
11-10-2006 16:16:18 [340]: (MI): Batch Adding Message d(Wed, 11 Oct 2006 19:45:38 -0000) fid(002)
11-10-2006 16:16:18 [340]: (MI): Batch Added Message rid(1)
11-10-2006 16:16:18 [340]: (MI): Adding Appoinment d(Wed, 11 Oct 2006 20:07:26 -0000) fid(010)
11-10-2006 16:16:19 [340]: Clearing internal progress log entries
11-10-2006 16:16:19 [340]: Entries cleared
11-10-2006 16:16:19 [340]: Unknown exception occured, skipping to next mailbox
11-10-2006 16:16:19 [340]: Waiting for work
11-10-2006 16:16:19 [340]: Worker thread exiting


I also tried exporting everything from an Exchange mailbox into a PST file, even though this is not the ideal way to convert alot of users. But when I try to use the ZCS PST file import wizard, it runs and finishes ok, but it puts "Sent By: Unknown" in all the From: fields of the converted email messages.

Any suggestions welcome.