what are the exact first 4 characters and the exact last 4 characters of your "text"? I've been trying to figure out what format it is in... and I'm wondering if there is more to this that we realise from your description.
Again, obviously, don't post the whole thing as it is apparently only protected by a 12 character password

this is what the tex looks like
AQAAxxxxxxx+AAUxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxR0RR