While migrating my MCMS 2002 database to MOSS 2007 I experienced a hang situation in the export step. Even after a couple of hours no progress was visible. No CPU was used by any related process and no filesystem activities was visible.
Finally I received a note from the product team that this is a known bug in MOSS 2007 beta two which is fixed in some later builds. The MCMS 2002 database needs to be hosted on a SQL 2000 server in order to let the export step work correct. The MOSS 2007 databases on the other hand can savely be used on SQL 2005.
It seems to work fine with me. I have MOSS 2007 Beta2 on SQL 2005 and MCMS 2002 SP1a.