This happened to me a lot when I was testing my Samsung admire. and it only happens when
1-you alter system folder files. (requires root access)
or
2- a program does system alteration. (requires root access)
to fix this problem try the following
1- Do factory reset (by turning off the phone *wait till it's off* and than hold on power + Volume Down + Previous Button .... Reset and clear cash.
2- If that did not work return the phone to corporate for a new one, I think they will only charge you $10.
3- If you can't get to a corporate store upgrade your phone to 2.3.6 (this will let you use the phone and text-messing only +web over WiFi.
MetroPCS Data and MMS will not work for you, yet this is the quickest way to get you back to your phone talking and texting (it takes around 2 minute to complete) to do so remove your battery and place it back in the phone, plug in the usb and keep on holding the Camera button, Odin service should pop-up pres volume-up and run the update tool.
for more about the 2.3.6 update please read the following
http://androidforums.com/samsung-admire/454073-regarding-2-3-6-update-metropcs.html