Decided to start a new thread about this problem that a growing number of users are having specially with the iPhone 5. It is unclear if this is just affecting Verizon and Sprint (CDMA) customers, however a small few have mentioned they are having problems over AT&T (HSPA+ or GSM).
With cellular data turned on (even if you're connected to Wi-Fi), users of Enterprise Exchange email accounts, the push feature eventually crashes. This causes other problems, such as: sending via iMessage and other app notifications fail. By turning off cellular data completely and connected to Wi-Fi, there are no problems at all. (To restart the push service, you can either reboot or simply turn Airplane Mode on and then back off)
There have been multiple 'fixes' mentioned on different forums, but every single one that was mentioned I have tried to no avail. I have also had my phone replaced at the Apple Store and did nothing to it except for adding my Exchange account. Guess what?? Same exact issue. A couple of users claim that putting the phone into DFU mode and doing a restore that way fixes it, but this does not work either.
This problem seems to be an iOS bug that is tied to the new LTE chip that is in the new iPhone 5. Of course these chips are not in the older gen iPhones, and iPads, etc., so upgrading to iOS 6 on these devices does not cause this same issue.