What the heck is "npvhash=4095"? I've been using Mac for 15 years, and I've had relatively few problems.

Many years ago, I was using a MBP 17" which sometimes was completely freezing: the only way to wake it was to hard-reset it (hold down power button).

This is where I met "npvhash=4095" for the first time, watching in my log files. Back then, I googled it and found a thread in Apple support forums where a kind guy told everyone who had this problem to open the font book, select all the fonts, right click, click "validate fonts" and delete all those which didn't passed the validation. That solved the problem. Now it doesn’t!

I'm on an 27" iMac with Snow Leopard 10.6.8 installed. Whenever I play Halo, after a few minutes, I get "npvhash=4095"—system freeze, until I hold down power button.

Of course, I've validated all the fonts with no result.

Does anyone know what npvhash means? If you don't know how to fix my problem it's not a big deal, I just want to know what is npvhash! I hope anyone can help me.
The boot process usually starts with npvhash=4095 in kernel.log.

And you can find #define NPVHASH 4095   /* MUST BE 2^N - 1 */ in OS X kernel XNU source code pmap_internal.h.