[Freesurfer] License problems

Hi all, We've just installed Freesurfer and tried to use mri_convert and encountered some problems. In the csurf GUI, I tried to convert a subject's image, which we keep in analyze (.img, .hdr) format, and I got the message: "Convert (subj186) failed - working on: orig/001/subj186.img" I then loaded the flat files (I.001, I.002 ... etc.) into the directory and tried to convert these. The program hangs indefinitely once I press the convert button. Next I tried to run it thought the command line on the flat files and got a message saying "No valid license key!". To the best of our knowledge, all the license files are where they should be. Any ideas on what's happening? Thanks, Alex