give it time .. 
i had to work around some parameters for the v8 of my stable router to get dd-wrt loaded.. drawback was i had to j-tag some stuff (at that time, killing linksys wasnt possible with a soft-solution). so i tested with a refurb (half price) model first in case i bricked it.
only drawback is i could only load MICRO version of ddwrt.. ([email protected] are getting anal about these things)..
hmm, i can tell u that with a cable modem OR dsl modem in place, a NONrouting, NON wireless model, u need a physically-connected box (computer’s ethernet port, a wired/wireless/combo AP, full router with wireless ability, etc).
your “outside link” device (cable/dsl modem) needs to be wireless/or a wireless router (with cable/dsl modem built into it to talk to outside world) if u are trying for two devices..
i had 3 devices in place, because location of my cable wasnt movable, (factor 1) location of my already-in-place-wireless router connected to my cable modem wasnt movable (factor 2), xbox 360 with tv couldnt be moved from living room (factor 3) and if equipped with microsoft’s usb dongle for wireless it would have cost about $120 CDN at that time.
cheapest device to run dd-wrt (that would allow wireless radio mode to turned into an AP/bridge/client-bridge/repeator-bridge/modes) was a linksys router at that time available for $29 with tax (refurb).
my scenario was to be able to connect xbox with my exsiting setup (wireless router connected to NON router, NON wireless cable modem). after that i could play xbox live, or run media off my computer on my tv. . .
tell me whats ur objective ? cable modem being one device, u want 1 more device to connect EVERYTHING to internet ?