Here’s an interesting one that we’ll be watching closely. Apparently the OS4 software update for iPhones recently released by Apple is causing problems with some Exchange servers. I’m guessing that the more iPhones you have hooking into your Exchange server the more likely this problem is to occur. Apple has released a quick and easy patch for the problem, but the patch must be installed on each iPhone individually. See the link for more details.

http://support.apple.com/kb/TS3398