Freezing Unresponsive seems to be a common problem.
I know around six people that have this phone including me.
All of them claim the device has frozen and become unresponsive without warning, I got mine a few months after them and haven't had the problem once.
Could this be a firmware problem with the older models?
there were many firmware problems with this phone. but as always on those kind of phones - there are also external problems - apps, games and other crap can sometimes render those phones useless.
you should check LG.com (there are many different versions for this phone, if you find nothing on the lg site, use google and you find your update)
one common thing about phones - resetting them helps most of the time - kick all the crap out and the device works ;-)