exactly the same thing happened to me... i suggest that you flash 42R_for_all if you have R372 or another monster pack if you have R373.
Just power the phone by simultaneous pressing
* +
# +
Red button (by doing this you will enter in bootloader) and connect you phone to the pc... it might ask to install some more drivers... install them and enter Flash Backup 2.62 or RSD Lite (as you wish.. both of them are good programs for flashing). Now just flash an mp (42R_for_all if it's your first flashing process)
If there's still no success with the normal key combination... try a force boot
Force BootLoader:
You will need:
-2 needels
- your mobile
- will of forceing it('cause it's a bit hard for the first time)
-OPTIONAL: Third hand or help of friend
Step 1:
Take away your battery from your mobile
Step 2:
Take 2 niddles and and make pin 4 and 5 to marge via niddles(I do not know english good enought to write it another way)
Pins 4 and 5 are red pins on this picture
Step 3:
Put your battery back in your mobile pins must be still marged(here you will realise why you need 3 hands)
Step 4:
Take away niddles away and check if there is a BootLoader in the screean if not go back to Step 1 if yes flash mobile