Hi everyone :)
First I'd like to thank all of you who are working on solving this issue - what can I say? You're great! I followed this thread for a while now and tested the latest posted version of the FSUIPC.dll. I am using UTLive and I have set (for the purpose of testing) my traffic to 100/100 (commercial/GA) and did a flight with RC4. The second last version of FSUIPC caused a strange error message from RC4. Upon acknowledging it, RC4 continued as usual. But on a second flight (FACT-EDDH) P3DV4.5 crashed. The windows error reporting indicated the fsuipc.dll as before.
The latest version working in so far, as P3D didn't crash (a re-enactment of the previously unsuccessful flight FACT-EDDH) but RC4 just died. The flight ended uneventful and rather quiet (no ATC is quite nice). I don't know it this was just a coincidence or if it is still related to the AI-RC4-issue and hence wanted to report my findings.
TL;DR: this latest version of FSUIPC.dll caused RC to quit but didn't crash P3DV4.5
Cheers,
Peter