Just got a new router so I can have wireless N and now I can't SSH internally. I've checked port forwarding but that's for external access anyway. The firmware has something called Access Control Management, but it's by default off.

It's a Rosewill RNX-N300RT, which according to NewEgg feedback is a rebranded WR841ND.

Any ideas, or should I get DD-WRT on it first?

Oop! Misread it -- deleted.

port forwarding is only used when trying to access certain computers on the internal network from the outside world. That's not what he needs.

OP - are there any log files in the router?

Yes but they're all from today and all DHCP related. When I get home I'll try telnetting and SSHing to see what it generates.

It seems to me to be a firewall related problem, but there's nothing in the "Security" section relating to port 22. "SPI Firewall" shouldn't affect this AFAIK.

Got DD-WRT loaded and still didn't work. Turns out my file server somehow got its IP address taken over by another device. All cool now, thanks for the help.

That's a hard problem to track down, but explains the symptoms. One thing you might want to consider in the future is modifying your DHCP lease range in the router to some subset of 1:255, and use the remaining address range for setting static IPs. That way you never have to worry about the router assigning an IP through DHCP which you (in your mind at least) have reserved for another machine.

For example, I have my DHCP server in the router set to only assign DHCP addresses from xxx.xxx.xxx.100:199, then I use the 2:99 range for static IPs for servers, laptops, etc., and I use the 200:255 range for static IPs for network printers, NAS, etc. Keeps everybody off of each other's toes.