Attempt to assign property of non-object

Click on the 'Compose' tab and I see this:

    * warning: Attempt to assign property of non-object in /path/to/website/modules/privatemsg/privatemsg.module on line 1489.
    * warning: Attempt to assign property of non-object in /path/to/website/modules/privatemsg/privatemsg.module on line 1490.

Any ideas here?