Keith,
If the process is hung, you may be able to delete the share on the file in question. If that does not work, and it is not an inconvenience, take the server down and restart it. That usually resolves any really stubborn locks.
If you still experience the problem, you may have a corrupt workstation file. To fix this, get the Computer Name having the problem, go to the mas90\home directory on the server and edit the fid0map.ini file with notepad or any text editor (fid"zero" not fid"Oh"

. You will find the computer name with a terminal ID next to it. Change the terminal ID to another one not being used by another workstation. Be sure to just backspace out the old number, and type in your replacement. Then save the file. Don't hit enter or add any other characters, spaces, etc. Go back into MAS using that PC. You will have to select the default company since MAS thinks this is a new PC logging in for the first time. You may also have to change any preferences for that workstation using file, preferences. Then rerun your report.
One final note: We have experienced a similar situation when we access a client network through Terminal Server and modify a file. For some reason, the file security is changed. Even though the folder and specific file is set to inherit rights from parent folders, which by the way have full rights, a look at the file's security properties shows that the Everyone group has been dropped. We edit the file right as Admin and everything works fine. (At least until we modify it through terminal server again)
Hope this helps. If not, let us know what the results were from the above suggestions. Also, the name of the offending file would be helpful.