Mine has not locked up totally. Occasionally it got choppy and I would always look up to the top bar to see the phone was transmitting and receiving data at that time.
Once I installed Advanced Task Killer that seemed to remedy the issue. I don't like it that certain apps seem to perform tasks even if not activated, such as Yahoo Messenger, Skype, Amazon, etc. I don't use these apps and I believe I will just delete them and give the phone battery a break from also these unnecessary tasks.