Vax
Occasional Visitor
My personal recommendation to flash Tomato on top of the original firmware:
1) Reboot in recovery mode (keep reset pressed while turning the router on)
2) Flash Tomato using the recovery tool
3) After it's completed, turn the router off. Press WPS, turn it back on while still pressing WPS. After 4-5 secs the power LED should flash - release the WPS button.
This is pretty much the exact way described in the guide. I followed it exactly and had no problems at all. Important to note is that some cable modems need a reboot or shutdown for a couple of minutes before switching routers because they cache the MAC address and won't recognize the new router then.