OP wrote above:
"Here is a strange one: I have ran the M.A with the original drive attached via a an USB/SATA converter (disk upgrade), and the M.A kind of stuck like its waiting for the drive.
But i can access the drive without a problem, i can even boot on it."
An IMPORTANT QUESTION:
What version of the OS is on the old drive?
If it is 10.4 (or older), Migration Assistant to a new OS won't work. I had this same problem when I tried to migrate from 10.4 to 10.8 -- simply wouldn't work.
In my case, I was able to upgrade the old OS from 10.4 to 10.5, and then it worked.
However, if your old Mac is dead, you may not be able to to that route.
In that case, if it's acceptable to you, I would recommend a "manual migration" of your data, and a "fresh re-installation" of your apps.
I would recommend that you create a NEW account for yourself (and anyone else who might be using the new Mac). You'll have to manually move items into it.
There are some special considerations when trying to "manually migrate" from an "older" home folder into a "new one".
Be aware that you CANNOT simply "copy" the main sub-folders from the old home folder into the new one.
By "main sub-folders" I mean the ones named Documents, Downloads, Mail, Movies, Music, Pictures, etc.
What you need to do is this:
For this example, I will use the "Pictures" folder
Have your NEW Pictures folder visible (the target).
Open your OLD Pictures folder (the source).
Either select individually those items you wish to move, or you might try "command-A" to select all the items in the folder.
Now, "drag n drop" the selected items into the NEW Pictures folder.
Check to see if this has worked.
You may need to re-direct the iPhoto or Photos (or Aperture, etc.) app to the new home folder.
If this works for you, repeat with Music, Movies, Documents, etc.
If you try this, please followup here to let us know if it worked.