On Tue, 10 Nov 2009 10:00:24 -0800 (PST), Tom
wrote:

Are you *absolutely* sure you're turning the arbor nut in the right
direction to loosen it?

Yes! And I did try both clock and counter clock wise.

The easiest way to determine is that an arbor nut turns to tighten in
the same direction as the way the blade turns to cut wood.