Recently, after upgrading my Office to Outlook 2010 64-bit, I plugged my phone in to my standard weekly sync with my Outlook, and up popped a message along the lines of "wrong outlook client". At the same time the sync (or lack thereof) process deleted all my contacts from my phone. After a very quick search I soon dscovered that this is a known problem between WMDC and Outlook 2010 64-bit. The official statement from Microsoft is this: Question/Issue "Windows Mobile Device Center (WMDC).....