When using message filters "Run Now" is often greyed out after running a filter and remains greyed out after the filter has completed filtering. (Hung up?) This does not happen if the filter does not find any matching messages. Clicking on another filter and then returning to the first one returns the "Run Now" button to active (not greyed out). Not sure, but the problem might be associated with filters that copy a message file to a Local folder, or delete messages, or move messages to Trash, or all three. I'm stumped. The problem started recently and I'm not aware of any changes I made to Thunderbird.