I am using nokia 7650 on my tests, i'm not sure does it happen to other handsets, but you can try it out. What i'm sure is it DOES happen to the "Blockgame" that Nokia shared as code example.
Here are the steps to inflict the bug:
1. start your j2me game and play it
2. get someone to call you
3. answer/reject the call, unpause your game and play
4. quit your game and exit the application
5. try to launch your game again
Voila! you'll have "System error". You can't run the game, you can't delete the game, the only way to rectify this is to "reboot" your handset.
It even happen to the commercial j2me games that i tried.
Any feedbacks from Nokia? or fellow developers?