I did exactly that, but as I say, although PF3 then does not bring up any error messages, when I contact ATC, I get the little 'beep' (I have that set in options, so I know that PF3 'received' the instruction), but there is no verbal response, no matter whether I choose ground, tower, clearance, or whatever. Just silence. Not even (in Remote Text) any notice that I am tuned to the wrong frequency.
Even though the COM frequencies that show when I hit the Tab key (the 'hint') are all present in PF3-FS9_Freq.dat, maybe I could try adding them again via the PF3 options menu. I'll try that today and post another log if it doesn't work. Thanks.