I found that sometimes the program seems to go into an endless loop if I respond to the "mask with other contrasts" question too quickly. If I wait for the contrast window to close, and the arrow to position in the 'no' box first before clicking, the program runs okay. Is this the same problem that the original post was referring to? This problem is probably hard for those who have fast computers to replicate. Simon Au Young MSc Program, Expt Med University of British Columbia %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%