I had similar issue when updating to 266 FW.
Let your phone 30min on wall charger
Try to flash only kernel with flashtool
If it success, you may be able to charge your phone, and after that make a full flash with flashtool.
It took me 2 days to solve the "brick".
If Flashtool doesen't prompt, try pushing the back power off button when entering in flash mode (vol down)