2 things:
1) Are you getting error messages or does ppm just hang?
2) If you access the internet thru a proxy you will need to set the http_proxy environmental variable.
I am getting no error messages...when I type ppm in the command prompt...it skips a line and then the command prompt shows up again. No error message shows up and also it does not start ppm either.
The internet access is the same for both computers...so it probably isn't the http proxy thing.