I had a very similar problem that I managed to fix, so I registered so that I could offer the solution.
First, make sure you have your IP set to some static address if it's not already. For instance, I had mine set to 192.168.1.17, and the default gateway to 192.168.1.1. Precise instructions can be seen here. Additionally, make sure to hold reset on the router long enough for the power light to be slowly flashing green (not orange).
After that, try flashing the wnr2000v3-factory_NA.img file from one of the earlier builds. You can look through them here. For me, ONLY the files from 03-08-12-r18687 worked, and nothing else. Every other version didn't play well with my router for some reason.