How can I fix Xperia x10i application crashes under CyanogenMOD 6?
I would recommend going back to the Sony official firmware.

This thread has step-by-step instructions for reverting Xperia X10 handsets to stock ROM.  You might want to search the thread to confirm that the process is the same for your X10i model before starting.

Keep in mind that flashing to the stock firmware will erase all of your settings and installed apps, so back up the important bits.