I recently upgraded to Act 2011 premium and have enabled the calendar sync for users with smartphones. For these users Act will periodically lock up, but for users that do not have the calendar sync enabled the problem does not seem to exist. The problem seemed to have gotten worse when I upgraded from Office 2007 to Office 2010, however upon going back to Office 2007, the problem still persists. I have disabled as many plugins from Act as well (such as our Dymo printer). Any ideas on something else to try would be much appreciated.