Nick, there are a lot of possibilities. I'm wondering what tutorial/instructions you were following when you started to run into problems.
Over at XDA there is a tutorial on the sbf process for the X2, which includes this set of instructions. Look at it carefully, as I think you may have missed a step or perhaps took a step out of order:
1. Reboot your computer and your phone after downloading and installing everything and before you go to flash the SBF file. Use 7-zip to extract the SBF file...
2. Once you have rebooted your computer, go ahead and start RSD Lite and point it at the SBF file and plug your USB cable into your computer ONLY!
3. Turn your phone off.
4. Turn the phone on by pressing and holding the POWER AND VOLUME DOWN buttons until you see FASTBOOT. Press volume down until you reach RSD and press volume up once.
5. Plug your phone into your computer and wait until you see it in RSD Lite and click Start.
6. Your phone will reboot when the process is complete. DO NOT UNPLUG YOUR PHONE FROM UNTIL THE COMPUTER UNTIL THE PROCESS IS COMPLETE.
7. If the phone boot loops pull the battery and boot into the stock recovery by pressing and holding power and volume down until the phone says FASTBOOT, once the phone says FASTBOOT, press volume down until you see ANDROID RECOVERY, once you see ANDROID RECOVERY, press BOTH the volume up and the volume down buttons. You will see the familiar triangle with the exclamation point and the Android. At this point press volume up and down simultaneously again and select