MW2 (360) says my NAT is strict but network test shows no problems?!?

ok so, on the xbox live menu on mw2 says my NAT is strict, and takes a dozen+ cycles through the matchmaking percentage before finding a game, and it is extremely frustrating. whenever i go to network settings and run a test, no little yellow sign pops up, no warning, no issues whatsoever. i have reset my router (netgear WGT624 v3) multiple times, as i have had this problem for a month or so. i have called my isp, and idk what to do about it. so please, give me advice on a long term fix, or a short term fix thats quick and simple that wouldnt be a problem doing as many times as necessary. please answer as if im a 5 year old, my network lingo is not very exquisite :p. please and thank youuu!