I have tried the solutions presented here, yet nothing has worked. I have a Microsoft Office 2003 install that was flaky, I uninstalled, rebooted, and reinstalled but the SBCMSYNC error persists. I have deleted the extend.dat file, and have also deleted the registry key, yet they both get recreated each time Outlook 2003 opens. I have applied sp3 to the install and the latest Office security updates. There is no Small Business Contact Manager installed either on the server, nor on this particular users system. Does anyone have a fix that will eliminate the registry key and the extend.dat file from being recreated every time Outlook begins?