Recently, I had an issue with the Windows Phone 7 to install the latest available update (the one related to certificates stolen).

The installation always failed with the error code 8018119C, meaning the system was unable to download the update.

I finally took some time to resolve the issue and found the MS KB related for troubleshooting Windows Phone update issues http://support.microsoft.com/kb/2484484

The solution for this error code was to restart the BITS Client service and cleaning the cache (run bitsadmin /reset from a command prompt).

In the same time, I discovered that it solved also another issue I had with Outlook 2010 and my Exchange mailbox. I had frequently synchronization error messages saying that network connectivity blocked the connection as well as the download of my OAB.

So next time you have trouble to download OAB from your Exchange server, try to clear the BITS cache.