If i THEN bring up 7.1 (from different directory
while 6.35 is running) then ident works!
The IDENT server is actually separate from the rest of the communication. If you don't enable "Only when connecting" (or even when you do, but two connections are close to each other), then the mIRC 6.35 client acts as an IDENT server for all IRC connections you make, including the ones you make from other computers that are connected through the same router, and therefor have the same global IP.
That should explain why your IDENT did work when both 6.35 and 7.1 were running.