Kernel Panic with new HDD

Okay, hopefully someone can help. I am lost. I have 2 "mid 2010" macbook pros. The hard drive crashed in one of them. I purchased a new 500GB drive (replacing the original 250 GB). I formatted the 500GB drive with MAC OS ext journaled file system. I installed the drive into the macbook pro. Turned on the computer, inserted my Snow Leopard disc, shortly after, kernel panic "You need to restart your computer.......". I restarted, same issue. I tried restarting holding down the option key and the only thing that shows up is the installer dvd, not the hard drive. If I click on the installed dvd, a minute goes by and then the kernel panic again.

I removed the 500GB drive and installed it in my other macbook pro and I was able to install snow leopard without any issue. I removed the drive and put it back into the laptop that started all this headache and bam....kernel panic.

The weird part is, if I take the drive out of my working macbook pro and install it into the macbook I am having the issue with, it boots up with no problems.

What could be causing this? PLEASE HELP!!

Not the cable. When I take the hard drive from the working Mac and install it into the "broke" Mac, the hard drive is detected and the Mac boots like it should.

On a whim, I took the 500GB hard drive (with the fresh install of Snow Leopard), put it back into the working Mac, performed ALL software updates available.

Put the 500GB drive back into the broke Mac, and it now recognizes the hard drive and boot like it should.

I've got it working, but, I do not understand how the updates made the drive recognizable?

Any further thoughts would be greatly appreciated.