Time Machine Backups Stall

This happens on 2 machines, a iMac running Lion and a Mini also running Lion.  They are both going to the same MBL that has the latest  firmware.

After a reboot the backups seem to go fine, then after a while or maybe because a big file is involved, this time a 40gig file, it just stalls. It has been stuck in 5.38 gigs of 43.2 since last night. 

Does anyone else have this problem? Is it a Lion problem or a MBL problem? Any Suggestions?

If I had to wager a guess I’d say it’s a Lion issue - the My Book Live is a really solid drive. Is it always the same file that is getting bogged down? What did Apple say when you contacted them about the issue?