My experience with PPM is that it didn't really like being behind a proxy/firewall, that could be one problem.
Alternatively someone might have tampered with the repository in which case you will need to make it point to whatever AS defaults it to do for example set repository MYREP http://www.ActiveState.com/PPMPackages/5.6 from the PPM
Last you could just install the package yourself by downloading if from Activestate repository archive @ http://www.ActiveState.com/PPMPackages/5.6/zips , then just uncompress in temp dir and run 'PPM install packagename'..
on the other hand a supersearch for 'PPM' should give you the same answers and a lot more