Problem uploading a sketch to ATMEGA644

I have a custom board with an ATMEGA644 (not ATMEGA644P) as MCU and uploaded ATmegaBOOT_644.hex bootloader (I got it from http://code.google.com/p/arduino-atmega644/) via ICSP (with AVRStudio). I used the fuse/lock bits from the enclosed boards.txt file.

atmega644.name=ATmega644
atmega644.upload.protocol=stk500
atmega644.upload.maximum_size=63488
atmega644.upload.speed=38400
atmega644.bootloader.low_fuses=0xFF
atmega644.bootloader.high_fuses=0xDC
atmega644.bootloader.extended_fuses=0xFD
atmega644.bootloader.path=atmega644p
atmega644.bootloader.file=atmega644p
atmega644.bootloader.unlock_bits=0x3F
atmega644.bootloader.lock_bits=0x0F
atmega644.build.mcu=atmega644
atmega644.build.f_cpu=16000000L
atmega644.build.core=atmega644

I managed to upload .hex files via ICSP - AVRStudio.

The problem is uploading sketches via ARDUINO IDE (via FTDI). I followed sanguino instructions to copy the folder to Arduino but receive this error message:

avrdude: stk500_getsync(): not in sync: resp=0x00
avrdude: stk500_disable(): protocol error, expect=0x14, resp=0x00

Is there any hint?

Many thanks in advance!

Doesn't the 644 require stk500v2 like the Arduino Mega?