Enabling http, https, telnet, & ssh causes telnet & ssh login attempts to hang making login impossible. Web access does continue to work. Rebooting the router doesn't help because it seems to be inaccessible from the very beginning.
Manually restarting telnet/ssh via the web gui sometimes fixes the problem.
Disabling https fixes the problem. Or setting http, https, ssh, but no telnet also seems to fix the problem (i.e. ssh login is possible).
Using an Asus WL-520gU with TomatoUSB OpenVPN (2.4 kernel). Version 1.27.8747.