If BusySync is unable to sync with Sync Services, an error may display alerting you to the problem. Typically, restarting your computer will "wake up" Sync Services and solve the problem. If not, you may be able to solve it by resetting your sync history, which will rebuild your Sync Services database.
Open the BusySync prefpane, select the Reset tab and click the Reset Sync History button. Then wait several minutes for BusySync, Sync Services and iCal to get in sync.
