cannot install freebsd 6.0

[Stephen Krauth]

I'm unable to even boot the FreeBSD 6.0 install CD (i386 version).  I have an 
AMD64 with an Nvidia nForce 3 250Gb based motherboard (MSI K8N Neo Platinum), 
currently running 4.10-RELEASE. The 6.0 boot cd dies with:

   panic: pmap_mapdev: couldn't alloc kernel virtual memory

This happens right after the agp0 load message.  I tried disabling ACPI with no 
luck.

Please help!  I've been a FreeBSD user for almost 10 years and it would be 
disappointing to give up now...

- Steve K.