Actually it states that you need to be on the newest 2.3.4 build right in the original post. Seeing as how the ONLY way to get the 2.3.4 build, aside from OTA soak test, is the SBF file, it's common sense that you would have to use RSDlite to flash it. The build you were using was NOT an X2 build, it was an Atrix build that was ported to the X2 by navenedrob on XDA.
Whenever your flashing roms, you need to be extremely careful and thoroughly read up on the process. With the huge variety of options out there, it is even more critical to pay attention to what you're doing because it is very easy to soft brick a device. If you are not familiar with SBF and Fastboot files, and RSDlite I highly recommend getting acquainted. These are the closest thing to a fail safe that's out there.