That's a pretty nasty choke, it sounds like. I'd recommend checking the logs, like citizen_elah said, and then I'd probably start removing a line from the rule at a time until the rule begins working again. If you can narrow it down to a particular line or a couple lines, it'd be far easier to identify the actual problem.
On another note, since your rule looks correct, I did a little digging to see if there are any known issues with this sort of thing, and found that other folks have had similar problems on 9.1 and 9.1.1.
Click here
You might want to contact support to get the hotfix in question, or look at upgrading to a newer version if you continue to have trouble after your debugging attempts.
-Colin
Nimbostratus