nooby firewall question

i have a Linksys WRT54G, and for some reason its built in fire wall is limiting my connection to the internet. I went to the command prompt and pinged google. only 50% of the packets made it to my computer, so im getting some connection but the firewall on my wirless router it obviously limiting it. I know this because the connection is fine if i bypass the router.

i dont really know much about routers, so detailed help would be appreciated

thank you for you help!