Are you on a network?
PowerPoint and the other Office apps can run into all sorts of network-caused or network-related problems. If you're having PPT problems and you're on a network of any sort, check your network vendor's web site for known issues with PowerPoint and/or Office. An updated driver might be all you need.
In particular, there appear to be quite a few problems with file corruption when PowerPoint saves to a Novell shared drive. Visit Novell's site and enter "PowerPoint" into the search box there to get a list of current known issues.
Until you get the problem sorted out, avoid opening and saving PPT files across the network. Instead, use Explorer or DOS or My Computer to copy the file to your local hard drive. Open it, work with it and save it there. Then when you're done, copy it back to the network drive.
Also: Always install a local printer driver rather than relying on network printer drivers. The local driver can be connected to a network print queue or printer, but the driver itself should be locally installed.