Triple Boot Windows 7/8 and Backtrack 5R3 issue

Hey !
I have two Windows (7 and 8) installed but i wanted get a new one,Backtrack 5R3, on my main computer.
So i followed these steps :
- Boot off Backtrack 5R3 LiveCD
- Partitioning my HDD like this "/" (system) and "/swap"
- Intallation of Backtrack with Grub2 on the "/" partition.
- Boot off Windows and set EasyBCD
- Add of Linux/grub2 entry
- Boot off Backtrack entry and see the Grub Rescue prompt that tell me there is "no such partition"...

This is how my HDD are configured :
/dev/sda1 (Windows 8)
/dev/sda2 (data)
/dev/sdb2 (Windows 7)
/dev/sdb5 ("/" /ext4 Backtrack)
/dev/sdb6 (swap)
/dev/sdc1 (data)
/dev/sdc2 (data)

Thank for the help.
I don't know what to do more...
Last edited: