We had the same error with several users in cached mode. How we
determined the problem was to first create a new PST file, connect to
it, then sync each mailbox older individually (click on the folder and
press Shift +F9), when you see the memory error, you've discovered the
problem folder(s). This is where it gets tricky, find the offending
item and move it to the PST file if you can and resync that folder. The
folder itself could be corrupt too. Repeat this for all the folders in
the mailbox. You may have offending items in other folders. If you
don't get that error you've found the offending item. Our offending
item was an internal email. It was 2mb w/o attachments. Once we deleted
it, the memory problem went away. Don't get discouraged, it'll take
time. What I did was to put the end user in non-cached mode and
recreated the mail profile on a test box in cached mode to troubleshoot
the problem.
Good luck and practice safe computing!
Art
MCSE
"Remember, there's nothing we can solve"