Thanks Pichlo for your advice and sorry for my late reply,but till now i can't boot my n900 after installing thumb2,i trying with:
flashing under linux first emmc,second combined
then i chech for errors:
umount /dev/mmcblk0p1
mkfs.vfat -F32 /dev/mmcblk0p1
fsck -af /dev/mmcblk0p1
fsck -r /dev/mmcblk0p1
mount /dev/mmcblk0p1 /home/user/MyDocs
restart
No any errors,then i try(i don't know how many times) to install thumb2,
everything looks good but when restart my n900 i had only black screen,nothing more,it does not matter how i trying to flashing my n900(for example recommended from Pali from the last post on this thread)i can't boot after install thumb2