LOL, coincidences... I did it just before you posted; force-rebooted the comp after some windows update got stuck halfway.
Opened it "the long way" (instead of "Recent Files"), manually compiled the FRED2 debug build by itself (no batch building)... compile...
1 file(s) copied.
0 errors, xx warnings
*blah blah blah could not find FS2PATH*
Earlier when I got the error it was actually my 2nd or 3rd compile.. and it just kept coming up. Don't know how it solved itself. also this isn't chief's new project - rather my own with the SAPI files put in place...
somewhere...

Definitely strange...

XD