@FritziE - sorry to hear you've a problem with Nimitz.
I presume you tried it more than once. Also, did you switch off your PC in between tries? If I encounter certain types of problem I usually try to start from a complete reboot - PC off, switch off power, pause, switch on power, PC on - to clear the cache and Windows detritus. Is it a pure B.A.T. install with no JSGME nor other mods? In the past I had 4.8, 4.9 modded, DBW, CUP etc all modded and occasionally experienced problems. I've decided, from now on, to stick with the experts and just use BAT as is.
I'm not sure whether the catapult mod has been improved recently (I know western is working on it, at least), so all I could think of for your problem was a corrupted Catpults.ini file. Just now I tried a Catpults.ini without Nimitz settings but surprisingly still got a Hornet to manually engage on the port cat and shoot - so I've no other ideas, sorry.
@Gerax and Bombs - thanks for the help guys.