aaaaa~~ someone help me please

im still having problems with momentus xt. i had the same problem before (i brought it up here) but even after getting a replacement unit, i still get the same problem
basically, i cloned my system to the drive and it boots flawlessly over an external USB connection. after i swap it inside my macbook pro 5,1 it wont boot (? folder image). i tried a fresh OSX install, but somewhere about 10 mins during the installation i got an error (the report was very long, cant recall anything).
my 500gb momentus xt came with the SD23 firmware. i tried updating it to SD24 using the bootable ISO, but i got the error which goes something like model matched, but firmware not match or something like that. i tried the 'force install' method (typing some code at the DOS prompt, found it somewhere in macrumours) but it still didnt work
im on EFI 1.8. some reports suggests that downgrading to 1.6 would solve it but at a slight loss of speed. i just tried downgrading, but the Aluminum_MacBook_Pro_Recovery.dmg file probably only works to downgrade 1.7 to 1.6 but not 1.8 to 1.6 (i cant find anyyone mentioning it works for 1.8, only 1.7). after restoring the dmg to my flash drive, my mac could not boot the flash drive (gotten the circle with a slash icon)
since this is my 2nd unit i doubt that this is the drives's fault. any help?