Interesting problem situation ... sounds like you're handling it with tact ... but maybe Erik and I can help with a tech consult next week.  

Is "scratch disk" your description or part of the system terminology?  (What sort of system is this, anyway?)  Have you run across the pre-Internet computer saying "always mount a scratch monkey"? 

http://www.science.uva.nl/~mes/jargon/s/scratchmonkey.html