ok, I understand.
It is possible that you set up the Mac Filter, that the IP addressed changed on the PC for some reason.
I would do this, reset to factory defaults. You should get access to the router then.
If so, then I would setup static IP addresses for your devices on the router. This will help make sure the IP addresses don't change and helps in troubleshooting. Make sure your getting Internet cleanly on each device.
Before you set anything else up. Save off the configuration to file. This can be use to re-load from this point on so you don't have to re-type anything.
After that. Then do some configurations. If you seem to get things going ok, save off the configuration again, rename it something else. Keep both files.
I would recommend that if you don't live in a high populated area or surrounded by other WiFi or have a lot of other devices around, that using default factory settings for security is probably best. I do understand peoples concerns for security however I have about 20 devices on my network along with WiFi and have never had any issues or call for mac filters. Yes they are handy and have there place. Just think about your system and the needs for it. The router can handle a lot and do a lot. I wouldn't over complicate it if there isn't a need for it. My 2 cents.