Here's a thread in the official help group (with Google Employees)
explaining it for two different people:
http://groups.google.com/group/Gmail-Help-Reading-Messages-en/browse_thread/thread/5371f8923e1b4544/e1a6a2889d6c2d99?lnk=raot
--
Bill Vaughan - "A citizen of America will cross the ocean to fight
for democracy, but won't cross the street to vote in a national
election."
Sadly, no - that would have been a reasonable answer. However, the
emails in this case are being sent from the Gmail SMTP server to a
Gmail IMAP account that is using the web interface. What makes this so
strange is that the Gmail to Gmail messages are usually near to
instantaneous. To have some mail delayed so much, and only on one
account, seems very strange.
Of course, telling a client "that's weird" doesn't inspire a lot of
confidence :)
Ryan