I was able to install openwrt. using the clean img and doing the tftpd thing. When I went to upgrade it, (using sysupgrade.bin) it said it couldn't recognize the file. So I picked the 3kb kernel file and it wrote that. But now my unit is dead. I can't tftpd the original clean file or any other file. Using 192.168.1.5 or 10.10.10.254. Now it just has a blue LED and won't do anything at all. 
If tftp is dead, then you'll probably need a flash writer, or perhaps a serial connection first, to verify its really dead.