in desperation, i called Tmobile and, without any options, was connected to HTC Support (surprise surprise). They were shockingly useless! i called 3 times before giving up. one tech support person asked me: "how did you get a G2?". I answered: "i bought it from Tmobile". They said: "huh?"
eventually, after trying to reboot, this, that, and everthing else i could think of, i uninstalled the gmail "app". i didn't even know you could do that. i then reinstalled it from the Marketplace. Now things work as they seemingly should. Time will tell. Whew.