Only other thing I can think of is that you may have a different Calendar specifically for your Droid and a different one for your PC. If this is the case you need to have the one from your PC synced to your phone.
This, ofcourse, if you have more than one Google Calendar.
If this is not the case then maybe you just dont have your Google Calendar (PC) synced to your Droid's Google Calendar.
If your not sure if they are, a quick and easy way is to check if both your Google Calendar, on your PC and Droid, show the same Tasks, or planned Events.
If you create a new Event on your Google Calendar (PC) does it update and show up on your Droid?