So which version is installed right now? Is it rooted (check with titanium backup) ? Can you somehow access recovery (clockworkmanager)?
As long as ur phone is rooted, try to access via command prompt and typing adb reboot recovery, while phone is plugged in. You can get adb from superoneclick (google) and going to its directory in command prompt.
Or install terminal emulator and type su
Then type reboot recovery.
Grab a zip from redy or huexxx in development, wipe data, wipe cache, wipe dalvic, wipe battery stats, go to install zip from sd card, choose zip, flash and it should be done. Once ur phone has booted, do a factory reset, reboot again and everything should be fine ;)
Sent from my blasting P970 with zeus :)