Jack, the point about the printer settings holding properly is a well-known and unresolved issue with Mac O/S, but not with Windows XP (for a change!) - so one would need to know which O/x svaughan is using to know whether this may be the problem - but the more general point about competitive management is correct - and deadly.
We also don't know what kind of monitor is being used - how old it is, CRT or LCD. If it is an older CRT, it could be starting to fade, so the same colour numbers would look "brighter" (actually more feint) on the monitor than they should appear in print. If the monitor calibration package is a good one and it is being used properly, it should not be necessary to intervene after the fact and adjust the brightness. The brightness of the monitor should be adjusted as part of the calibration, e.g. as it works with ColorEyes Display.
I agree with Tim Gray and Ray about the illumination conditions. I use a ceiling track of Solux 50 Watt bulbs to illuminate my work-space for print viewing. Makes a big difference even how the print is positioned or tilted under the light (with matte papers anyhow).
Something that can be elusive unless one has the habit - it is important to make one's final luminsity adjustments with Soft Proof active. Soft proof, if properly set-up, should come very close to replicating on screen the effect of seeing the relevant paper as if viewed by reflected light. If svaughan is adjusting his prints without soft proof, they will appear bright enough, when in fact they are not for the paper being used. He would only know this in advance by activating Soft Proof, whereupon most of the time the image darkens on the monitor, inciting the user to brightem it - and bingo, a brighter print emerges from the printer.