Are you sure you want to sync apps? All existing apps and their data on the iPhone will be replaced with apps from the iTunes library

If this error message pops up for you, right click your iDevice in the left iTunes column, click Transfer Purchases, then try syncing again. Learned that after running around several circles today!

I tell you what, the iTelephone made syncing a smartphone/PDA with the Mac easy again since the late Palm lost interest, but it's still far from perfect.