After a dismal server crash while attempting to update from Exchange 2010 to 2013 CU1, I created a temp exchange 2010 server to host the mailboxes. I recovered the mailboxes from the old server that had crashed to the new one. Mail was flowing correctly.
I then created an Exchange 2013 CU1 VM, moved just my mailbox over using the ECP. This worked fine. I was able to send and receive as well as hit OWA.
I decided to batch move several and only one actually completed after several hours.
Looking at the move requests using get-moverequest| get-moverequestsstatistics, I noticed that only one completed, some were suspended, and about 10 of them had an error of "stalledduetowritecpu".
I have tried giving an offering to Google, but did not return anything of any value on what that error could mean on a mail move.
I was thinking of editing the MSExchangeMailboxReplication.exe.config file to reduce the amount of simultaneous moves but I am not sure if this will fix that or not.