Scanning Multi-Page File Size

I load multi-function printers on field employee's computers. Since Vista is
beginning to show up on their computers, I find that after loading the
printer software everything works okay except when scanning multi-page B&W,
300 dpi documents. If I scan one page the file size is normal, around 65K.
If I scan two of the same page the file size is 1.2M. This is happening on
H.P., Lexmark and Brother machines so it must be a Vista driver problem.
Using these same machines on an XP computer produces multi-pages B&W at the
normal file size of a 200K or so. Does anyone have a solution for this
problem.