Although I have never had the problem I have seen similar threads and it appears it may be an authorization problem.
A couple of fix's that seem to have worked for others are, downloading a free app directly to your touch via wifi, it seems that having to enter your account information to download the app will fix the authorization problem. Deleting the apps from your Touch then connecting to iTunes and re-sync to re-install the apps, this takes a little longer but also seems to work but you must make sure that iTunes is logged into the account that the apps were purchased with before connecting.
Hope this helps.