In February, on a 400 MHz PII, I built gnome 2.4 under NetBSD 1.6.2ish.
I didn't have the 'hostname not resolvable' problem, but many things
were interminably slow.  Some programs would start after 30 seconds to
a minute, and some (evolution, nautilus) would not become usable even
after waiting an hour.  I upgraded NetBSD to current and performance
was much better, to the point where it was only a little slow.   I
suspect some library mismatch, as other 1.6.2 systems with gnome 2.4
ran ok.

So, I'd suggest that you delete all packages, clean out /usr/pkg, and
rebuild gnome from current pkgsrc.  With a 1.5GHz/512MB box, that
shouldn't be that bad.  Gnome 2.6ish should seem only the slightist
bit sluggish (after starting up your session, which might take 10
seconds to demand page in many megabytes of libraries) on your
machine.  I'm using it on a 933 MHz P3 and not being annoyed.

-- 
        Greg Troxel <gdt@ir.bbn.com>