I've experienced the "won't call" syndrome exactly as you're describing, but I didn't really associate it with how many text messages I'd sent out. Hmmm... I wonder.
But in my case, turning the phone on and off didn't fix it..I had to do a battery pull. Normally, pulling the batter out wouldn't be that big a deal, but it is DANG difficult to get the cover off and on with this phone.