exec() issue

Hi all, I've been having problems trying to get an exec() to work... There are basically two classes, one downloads then exec()'s the java runtime environment, the other does the same thing for MySQL. The Java one works fine. No problems there :-) The MySQL one does essentially the same thing but hangs. MySQL is distributed as a zip with setup.exe within it, so I'm calling exec() twice in succession but if I log the output, I can see the unzip operation finishing, and the call to "setup.exe" just sitting there waiting. If I then close my GTK window (terminating my own program), the setup.exe program will run! I've looked around, and I've tried closing my (nonexistant as far as I'm aware!) session before doing the 2nd exec() but this doesn't seem to solve the issue. Anyone else come across this ? Cheers, Simon