Powerpoint 2007 and computer freezing

[T]

I have an issue with Powerpoint 2007 freezing while users are making
changes to their documents. Sometimes the following will happen:
* User will get vertical lines when they type text on a slide.
* User will get memory address error and a message stating that
Powerpoint has to close.
* User will get a message stating that the OneNote printer is not
installed.
* And the most recent issue is that the user receives a message
"ipperr.txt is corrupt. Please run chkdsk utility.".

I have done all of the following (if not more):
* Installed new video, printer drivers
* Ran a memory diagnostic utility to check RAM. No issues found.
* Changed hardware acceleration
* Uninstalled/reinstalled Office 2007
* Installed Office SP2
* Wiped and installed everything fresh

This is in a lab setting and we're running Novell and WinXP Pro. All
of the computers have a printer installed via IP address, however
Novell iPrint is installed on the stations. The problems started
around December, prior to that we had no problems with Powerpoint
freezing at all.

Any help or suggestions are appreciated.