Just a guess: Someone has altered some security setting, may after a security patch has been installed.

Run Filemon for Sysinternals and see what is happening.
http://www.sysinternals.com/ntw2k/source/filemon.shtml

>We somehow developed this issue after years of running with no problems. Lately on all 20 computers running this code, we experience this behaviour :
>
>When a RUN command (that executes a DOS command, like nPrint, or a PGP command line call or calling a batch file that FTPs something) the DOS box freezes. VFP is obviously frozen as well but what's really weird is that WIN2k is sort of frozen as well. You can still click the task bar and move the mouse around but you can't run any new programs and if you try to kill the DOS window or the VFP program (assuming the task manager was up , because if it wasn't you cannot bring it up) the whole computer freezes completely.
>
>Any ideeas ? (we are working towards getting rid of the DOS code but there is a lot of legacy code hanging around)
>
>Thank you
>
>Sorin