Ok Never mind I found a solution.
the libparted version that comes with backtrack is old and has some bugs reading partitions created with fdisk (I can only guess that this is a specific version
issue cause I had no problems partitioning the drive from my native ubuntu system)
what I did in the end was completely remove the partitions from the disk(I did it from ubuntu but maybe u can use fdisk for these if you don't have , and use gparted (apt-get install gparted)
to create the partitions I needed. then the installation went throe with no problems