I DID IT!!!
finally i did it: i flashed march rom on 0,23c bootloader after 2 weeks of hard work.
for those have same problem just follow me:
FIRST OF ALL:
as GroovyG says
"You just need a SD card to update your bootloader, no need for the old flash tool.
Format the SD card, (with FAT file system) and put the three files for the bootloader on it:

chain.lst
EBOOT.txt
EBOOTn.bin

Make sure EBOOT.txt contains chain.lst, chain.lst must contain +EBOOTn.bin
Insert the card into your phone, reset it while holding the ALT key, and choose download image from SD card in the bootmenu. That`s it, it should update the bootloader now and restart automatically "

BUT

yoy have to press ALT key + SHIFT key
after pressing this 2 keys u will see the system boot from sd and start uploading new firmware.
then u'll can upload new OS through USB cable with flash update tool 0,3

JUST THAT
Thx to GroovyG and good luck to everyone

Nice find! I guess each single one of these phones behaves differently somehow.

Now, after the flash, does it run fine?

yeah thx,
it is fine now:
better gsm and good battery
thx again

can you just do a bootloader update without doing a rom update? also my chain.lst file has the name
+EBOOTn~1.bin

does that squiggly line need to be taken out?

is the c19 bootloader better than c23 one?