Today the Cruise stopped starting the mail/messaging client.
When trying to synchronize, I also got the message sync was not possible (error 80004005).
After few trials, I had the bad idea to follow common suggestion, thus remove profile from activesync and try again (not working) and restore backup done some days ago (again, not working).
Likely, before going with an hard reset, I had the lucky idea to remove the sd card: bingo! Outlook is now starting.
So, the problem is in the outlook directory in the sd card that somehow got corrupted (it is where attachments are put).
So, solution was: remove the directory in the sd card (outlook will re-create automatically a new one); that's all.
Unfortunately I discovered that too late (the backup restore have caused me loosing few data not backed up), but I hope this massage may help someone else having similar problems.