Rule update help

I have an existing rule that I am trying to update the timeframe. I have not updated, or added a rule in quite sometime. I am not sure how to fix this error. When I try to update it I get this error.

Probably your only option is to rebuild it from scratch. Anytime I have gotten an error like that you can't do anything in the editor to fix it.

Luckily it's a small rule so not much to rebuild. What I do, and I believe others as well, is clone any rule before I try and edited it, especially large ones.. That way if this occurs you can go back to the original and start over.