> I'm running NetBSD 1.5.1 on a Pentium 100 with 8 megabytes of ram.

it's much probably this machine isn't good. memory is the first thing to
check.

try disabling external cache in BIOS. if without ext cache crashes
faster/more often your memory is broken. if stops crashing - your external
cache is broken.

> is this just memory exhaustion?

i'm using netbsd on 486 25-66Mhz, 8MB RAM+12MB swap and got over 100 days
uptime on one machine. this machines are used for NAT, but some other
programs are on them.