Plasmas interfere with IR because they themselves give out huge amounts of IR (as do LCDs) so they swamp other IR transmissions and also IR extenders see the IR as a valid signal to be sending and also amplify it which is why you see the emitters permanently lit.

Plasmas do not interfere with 2.4GHz RF and so your plasma won't interfere with the signal between the iPronto and the NetXtender.

Phil