I would go to this thread, and download the zip in the first link (starts with PCIMG36).
Amon Ra Style Recovery for Supersonic - xda-developers
Put the file you downloaded on the root of your SD card, and rename it PCIMG36.zip
Download a rom you want. Any one. Put it on your SD card.
Boot the phone into the bootloader (hold down vol down, and power). It should ask if you want to flash the update. Say yes (I think vol up is the command). After it is done flashing, you should be able to select the option for recovery, and press power to select it.
From there, just do a wipe in recovery, and flash the rom your downloaded.
You could also probably go into the bootloader (vol down and power), hook up the phone via a usb cable, and run the latest ruu.