Process started by exec() function appears to hang; script times out.

I have two computers both exactly the same (supposedly):

Both are:
Windows Vista Home Premium SP1 32-bit
IIS 7 installed
PHP 5.2.6 installed via FastCGI

Both have a small VB6 program with a registered OCX file it requires to function.  The program does one small operation and immediately terminates itself.

So on one computer I do exec("theProgram.exe"); and it launches, does it's thing, and terminates, as expected.  Task Manager shows that user NETWORK SERVICE launches this process.

On the other computer, the very same PHP operation launches theProgram.exe and it appears in Task Manager, along with cmd.exe, both run by NETWORK SERVICE, and nothing happens.  theProgram.exe does NOT do the operation it was programmed to do and does not terminate itself.  If I load the script from a web browser there is a timeout that shows IIS didn't receive a FastCGI reply.  If I terminate the process for theProgram.exe, then the rest of the PHP script runs normally....   Manually double-clicking on theProgram.exe, verifies that it works fine by doing its function and self-terminating.  Running "php.exe myscript.php" from a Command Prompt, that contains the very same exec() function, runs theProgram.exe just fine and it terminates itself as expected.  This led me to think it's an IIS/PHP configuration problem, or something with the NETWORK SERVICE user credentials.

I exported the configuration for IIS from the computer where everything works as expected, and replaced the one on the problematic computer.  I also replaced the php.ini.  I also verified and re-applied all permissions on files and folders.  Nothing helped.

I've even uninstalled and reinstalled both IIS and PHP.  The problem persists...

Some things seem to work fine on the problematic computer, like if I do echo shell_exec("help"); then it launches cmd.exe HELP under NETWORK SERVICE and the PHP script prints out the response from the HELP command.  I'm just not too sure about it running Win32 programs properly.  I'm now thinking it's some sort of VB6 dependency problem... (???)