So even replacing the card results in the same issue that the Pi freezes and needs to be restarted?
Ok, some more things to try:
Can you check the PSU you are using for the Pi can provide enough power; You are best served with a PSU which can provide 5v @ 2A - so a high powered phone charger (as you get with a new iPhone or Samsung device, not a standard USB 5v @ 1.1A. If you are in doubt, Pi resellers do sell reliable PSU's.
I have had a similar problem, however I found that it was due to the R-PI being turned of unexpectadly, this seems to stop the R-PI from working and the way I got round this was to do a clean reinstall on the card after sds format etcher ect on the card, the problem only occurs when the power was interupted and Pi was not shut down from web interface. if your power supply has a intermitten fault this maybe the answer
1) Does it work when you go through a clean install back on the card
2) If the R-PI does not work, then their is a potential fault with the R-PI
3) If R-PI does work, the likelihood is that there is an intermitten fault with the R-PI power supply
4) My fault was by me interupting the power supply causing the failure! (therefore the fault was NOT with R-PI or softaware or even my Power supply)
Any luck this will give you a bit of help with your issue!