When you re-started mIRC (technically when you disconnected mIRC from the network), all online timers were automatically disabled, so none of the /timer commands in your script would still be running.
Do you have any of the following events:
1) ON CONNECT
2) ON JOIN
3) ON START
If so, please post the code(s), as these are the areas where the unban command would have to be issued from for it to work upon a restart.