If your company’s Microsoft Exchange server requires encryption, you’ll probably want to put the brakes on upgrading your iPhone to the new 3.1 OS. Users in the Apple forum are reporting problems logging into their accounts due to lack of encryption support. Some are seeing their access restored after a reboot but others are not. Rolling back to 3.0 hasn’t worked for everyone either. Apple has been alerted to the problem, but in the meantime, it’s probably best to wait until there’s a fix.
Per Apple’s list of 3.1 features, the only change to Exchange support seems to be “Improved Exchange calendar syncing and invitation handling”. I would guess the problem is connected to this, but that inconsistency with the reboot and rollback fixes make it sound a bit more complicated than that.
Via The Consumerist