Try disabling Aero in Vista.

Another fix is excluding the "send to bluetooth" add-in from the Excel options. Here is how to:
1. Open Excel from start menu.
2. Click the Office symbol in top left corner, hit Excel options.
3. Click "Add-Ins", then choose COM Add-Ins from dropdown menu in bottom of
your window and click Go.
4. Mark the line with Bluetooth in it, and click remove.