A big selling point for Research In Motion's Playbook is that it can link to a BlackBerry to manage email and contacts. But AT&T is blocking that very functionality.

According to CrackBerry, AT&T is blocking PlayBook subscribers from downloading one of the PlayBook's key applications, BlackBerry Bridge. The app, which allows BlackBerry owners to link their phones to the PlayBook,is meant to fill the holes in the PlayBook's functionality by offering users access to their BlackBerry's email and data connection.

But AT&T subscribers have found that they cannot actually download the app from RIM's App world. Instead, they are greeted with a message claiming that the app is not supported by their device or carrier.

That's a significant loss in functionality for the PlayBook, and likely not the best news to greet RIM on the launch day of its new tablet, assuming RIM was not already aware of the issue. Some users, however, have discovered a workaround, bypassing the App Store altogether. At the moment, Verizon and Sprint subscribers seem to be unaffected.

AT&T and RIM did not return calls for comment.