I have upgraded the router to your latest 1.1.1.06 firmware and after it reboots (which btw takes ages) it comes back with:
Critical failure. Please contact support.
Any idea on this? it is unusable now!?
From your description, "Blinking green PWR LED and solid red DIAG LED is all I get", the device is still at boot loader phase. So you tried tftp method but doesn't work? Can you try again? you can use this tftp.exe (http://tftpd32.jounin.net/) to upload the firmware to 192.168.1.1. Below are some more details about the tftp upgrade.
2.power on with pressing the reset button, wait for 10s, untill the diag LED turn red, and power LED keep flashing.
3.set lan pc to 192.168.1.100
4.use tftp client to put the firmware to device. Windows command for example: tftp -i 192.168.1.1 put RV32X_v1.1.1.06_20131206-code.bin. Or using other tftp client like "http://tftpd32.jounin.net/"
5.after tftp finish, the device will reboot by itself.
6.after startup, power led is on, diag led is off.