Nil return

Have to file a nil return-downloaded the latest X M L utility. Have entered the value of taxable services(less than 10 lacs and first year of filing ST return)and selected exemption notification 33/2012 .The sheet is still showing service tax payable instead of zero. As a result when I generate X M L am getting error message as difference between service tax payable and paid. What could be the reason for the error? Since it's not a showstopper and just a warning should I go ahead and generate X M L and upload it. Pls advise