We just ran into the same problem on a 60GB database that we were attempting
to restore to another server.  The problem ended up that the SQL server had
"reconstruction" processing that it needed to perform as part of the restore
and (in our case) was going to take from 4 to six hours.  The problem was
that our COMTIMEOUT server option was set for 300 seconds.  We performed a
"setopt commtimeout 21,000" (which is 6 hours in seconds) and it worked.  I
would just remember to set this option back to a lower number when you are
completed.