Printing problems at work

I work for as consutlant for a campus library and we are having a problem. There is a lady who thinks that aliens are the ones who killed JFK and other such things...so she spends half the day 6hrs+ searching though web pages and prints over 1000 pages in that time. I am not kidding.

The thing is this, these are HP 4350 laser jet printers, only 1 year old. They are used quite a bit by the 14,000+ students and other people, but i only get this problem when she come in to print.

What is going on:
When she starts to print everything seems to go well for the first few hundred pages but after a bit she starts having the ink speckel on the back of the page. It is nothing really bad and you can still read the page but she freaks out about it.

The question:
Can a printer over heat and cause this problem? When i open the cover and take the ink out there is ALWAYS a little pile of powder on the rolers. I take a printer vac. and suck it all out. I know it isnt the ink cart. itself because i replace it with a new one and the same thing happens.

Any help would be welcome. i just don't know what to think anymore. We can't replace the printers because it costs to much and the students will have to pay for it.

Thanks

EDIT: There is a charge that i forgot to write about of .04 per page or .07 for duplexing/ so she spends over $40 each time

Mmmm, consulting, a portmaneu of con and insult, as Dogbert once put it. I envy you.

A printer can always overheat, just like any other piece of very expensive, very refined equipment. I would lock her out of the damned thing, to be honest, or set a page-limit per day or per print job, above which you pay a surcharge per-page. (The latter is a societal solution to a societal problem, while the former is a technical solution to a societal problem. The latter will probably work better as you should address societal problems with societal remedies.)

I would tell her that the ink specs on the back of the pages are tell tale signs from god that aliens killed JFK and that she needs to stop printing so many damn pages now that she knows the truth.

Edit: the page limit per job sounds like a good bet