This was happening to me too, but here's what finally worked for me.
After syncing your iphone, click on the applications tab. Make sure the "Syncs applications" is checked. Then select "Selected applications". Now uncheck the affected app and then hit "apply" (on the bottom right of your screen). This will remove the affected app from your phone.
Now go back to the applications tab, and select "All applications" and then hit "apply". This will put the app back onto your phone and should correct the icon.
If you select "Selected applications" again, make sure to check the app that you want again or it will not put it back on your phone.
This is what worked for me finally after trying a lot of other things. Hope it works for you guys. Good luck.
Paul