I noticed today that I wasn't getting any email.  So I sent myself a test
email (from a yahoo account), hit send/receive, got the usual box saying
"receiving 1 of 1", it looked like it was downloading (but no green bar) and
then no email.  I checked all the folders, and it's not here.  I also
searched the entire computer, and none of the email sent to me in the last 12
hours is here.  I (eventually) rebooted, and windows mail is now again
receiving email as usual.  My ISP confirms that my email was downloaded off
their server, but there's no sign of it here.  

I know of at least one important email that was sent and did not download.  
Any thoughts on what may have happened and whether there's any way to recover
my lost bits?  (My ISP has promised to restore any email that was on their
server at midnight, but anything since then is gone.)