Hello. I'm running Mandrake Linux 8.2 here. I'm trying to use VNC
to remotely login to my box, but the port never accepts the connection...
it looks as though my machine is in stealth mode with my VNC ports
580x. Further, when I try to use the music-sharing client lopster, it simply
cannot connect outbound at all. It seems that both of these problems stem
from the iptables firewall.

Is there any easy way to selectively open specific ports so that these
programs can work correctly? I've tried to use Guard dog, but it isn't working
correctly.

I've had this problem forever now, any help is appreciated. Thank you.

first check your firewall

ipchains -L
or
iptables -L
iptables -L -t nat
to see what is blocked and what not

When you know what is blocked, you need to change the rules manually. AFAIK in MDK it allows you only to set up a simple firewall. Hmm, maybe it's a good idea to use webmin? I'm not sure if it supports firewalling, but I hope so.