Question : Exchange/OWA - Administrator

We were currently able to view users mailbox by navigating to https://exchangeserverip/exchange/username

However that stopped working all the sudden. The account we are trying to use is the domain administrator account which has exchange full permissions in system manager, and confirmed the permissions in AD are set to full mailbox access

Answer : Exchange/OWA - Administrator

Managed to track down the issue to the version of Powershell installed.  The Exchange post SP2 update rollups don't install with Powershell version 2.0 installed, I uninstalled Powershell 2.0 (which is listed as Windows update KB968930), installed the Exchange update rollup, then reinstalled Powershell from Windows Update.