Hi nofish, I've never noticed that one, but on more than just a few occasions I've had it to where actions seemed to just stop working. Most of the time it seems to be a SWS, Script, or Custom action.
Another one is that some hotkeys wont work when tied to "Misc: Pass through key to main window" if the Timebase is Synced to the arrange view.
I'll have to try the reselect "Midi Editor" thingy next time.