I just tested rdesktop (n900->win7) and vnc viewer (n900->snow leopard) and both work great (though vnc is SLOW for some reason) by IP address. In both cases I could not use the host name.

since you can't ping as a non-root user at all, I gainedroot and pinged both by hostname and ip. IP worked, and hostname did not. I then tried to ping www.google.com and that worked fine.

So that seems to be the crux of the issue. Perhaps the n900 is using the data connection for DNS resolution instead of the WLAN? I KNOW my router properly resolves the local hostnames with DNSMasq. Anyone have any idea as to a fix?