I had an issue trying to delete a rule. I selected the rule and hit the delete button but the rule just would not delete and there wasn't any error msg or anything.
After a few attempts I checked the log file and saw the msg:

Error during deleteRule: - System.Data.UpdateException
An error occurred while updating the entries. See the inner exception for details.
The primary key value cannot be deleted because references to this key still exist. [ Foreign key constraint name = FKRuleConditionRules ]

I removed the condition then the rule deleted correctly.

A small bug, but it would be useful to either know that you need to delete the conditions first or better yet cascade the delete down to the conditions.