I heard this tip a little while ago, and it really helped.
Basically, you put your cellphone in the freezer for about five minutes, and until your phone is room temperature again, you will be able to use your touch screen normally
. During that time, go to Menu> Settings> Phone> Calibration, and recalibrate.
If the calibration isn`t successful, you may have to reset it to its original factory settings, in which, freeze it for five minutes again, and then quickly transfer all files and contacts you want into your SIM card, and your pictures, videos, etc into your computer (you should have a cord for that.)
After you`ve made sure you have all your files backed up, type in the code: *2767*3855# to reset it to factory settings.
if your phone is STILL buggy, contact your service provider, and request a replacement phone.