When I had users experiencing similar issues, I had them turn off wireless reconcile for Contact/Calendar (depending on what the issue was), then do the RSET to clear the device database. Then enable wireless reconcile again. This will force the device to reconcile the calendar/contacts.
The difference between stupidity and genius is that genius has its limits.
When you take things for granted, the things you are granted, get taken.
Even a mosquito doesn't get a pat on the back until it starts to work.
Too many people miss the silver lining because they're expecting gold.
[BES 5.0.3 / GroupWise 2012 HP2]