what have you tweaked ? it doesn't work in a new scene from scratch ????
i would suggest first, restart your computer... who know... if not, go back to a previous stage of your scene and do the tweak again and check often to see when and where it stop working if it does.
Cheers
PS : for that you need to have previous version not to far
..... for all people reading. incremental versions before each big operation !!!!!! having your script Myscript_v35.mb is a security.