Limited or No Connectivity

are you running windows xp or vista? if so make sure that your DHCP service is running, and also make sure your IP address is configured to "obtain automatically" if your router is configured to do just that. Otherwise I would say:

1 - upgrade firmware
2 - make sure everything is configured correctly on router and pc (I suggest making same as other computers connected)
3 - uninstall and reinstall your network adapter or install newer drivers for network adapter.
4 - your router is bogged down due to the fact there is more than one computer connecting to it. It may not be built to work well with more than 1 pc, even though it is capable.
5 - your router is not within good strength connection of your pc.

- i can help you more if you give me more information and try the things listed above. but be careful when screwing around on the router settings, you could click something causing everything to stop working.