My router is suddenly not accepting incoming traffic from the Internet.

I can reach it via ping but not via traceroute (traceroute hangs at some hop associated with my ISP). I can also access the remote management port (i.e. :7080) for its IP address. However, none of the NAT ports I've manually opened up are routing traffic. All requests time out. Requests to the target addresses over my LAN do get routed correctly.

I'm certain it's not an issue with my ISP, given that some traffic makes it through. I don't have any security features enabled except for the SPI firewall, and disabling that did nothing. It was also working fine yesterday and I don't know what might have changed.

Is there any way to diagnose this issue further, or suggestions for what might be causing this? I can't find any useful information in the system log or traffic statistics.