Citrix server is being processed and the process doesn't complete properly. Vmover.log contains errors similar to the following:
Registry Error 1450 Insufficient system resources exist to complete the requested service. SOFTWARE\Classes\Interface\{F0B41FD8-1F1F-474E-B9D1-0FE580272E2F}\TypeLib (RegCreateKeyEx)
\\CITRIXSRV01 Registry Error 1450 Critical errors limit (1), operation aborted!
The registry has reached or is close to the limit. As per http://support.microsoft.com/kb/302594
Windows Server 2003 (32-bit): The System hive size can be up to one-quarter of the physical memory (up to a maximum of 200 MB).
On a Citrix server any computer connecting will leave a big list of printers in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Print\Providers\LanMan Print Services\Servers\ key that are not getting cleaned up and the registry keeps growing.
Turn off the registry processing in Migration Manager or contact Microsoft and Citrix in order to resolve the registry size problem.