Ok, i hope this helps to anyone who's having the same problem.
When cd installs boots at the install raid something or one harddisk pres ctrl+alt+f2, at the promt type the following:
insmod aha152x.o aha152x=0x340,11,7,0,0,0,100,0
Assuming your 1520B config is at plug and play config..
Now i have another problem to fight with but i hope this helps somebody.