There's probably some database corruption on your account, or you have some issues with your workstation. It's either one or the other.
To determine which one, try and see if you have the same problem on another PC. If you do, it's a database problem. Otherwise it may be a corrupt install that needs to be repaired.
Are you the GroupWise Admin? You'll need to run GWCheck on your user database (and maybe the entire post office) to repair.
Also, you need to patch GroupWise, you're about 5 major patches behind, which could also contribute to your problem.