first of all try putting the phone into recovery mode and clear the davlick and the ordinary cache and reboot.
If that dosen't work you'll need to re-flash the firmware for your model of phone, you'll need the samsung usb drivers available from here
SAMSUNG USB Driver for Mobile Phones v1 5 25 0 retail exe, odin v3.07 flash program availabe from here
http://forum.xda-developers.com/attachment.php?attachmentid=1168421 and most of all the firmware you can get from
Firmware archive Samsung Updates make sure the one you download is for your network and country.
1.install the usb drivers from samsung on your computer
2. power off the phone then put it into download mode
3. run odin 3.07 and locate the downloaded firmware it will need to be unzipped to a folder on your desktop before you can flash it
4. on odin
don't touch any of the pre-checked boxes, the
pda button click on it and select the firmware once loaded plug your phone into the usb port on your pc - where id: com window is - should turn light blue with a com port number, now hit the start button at the bottom and wait till its finished.
5. when the phone restarts unplug the phone and all should be ok
Hopefully you should be up and running again:-)
SAMSUNG USB Driver for Mobile Phones v1 5 25 0 retail exe