I do not think Samba is related to Linux kernel at all, Samba is a free software re-implementation of the SMB/CIFS networking protocol [quote from Wiki]
I am not finger pointing at all, just a bit of suggestion since Android users do may have better idea on Application level issues.
tho I too agree on your point 2, seriously agree on that..
Back to the question, it is possible to cross compile Samba server on Android, I have seen someone in XDA did that, which may or may not have solve your problem (CIFS on different OS/versions are tricky), give that a try.
Or the other way round, find a Linux box with Samba Client debug mode on and try connect to your Android, since in Linux you can "see" fully with a debug log to pin-point what might have been the problem on the auth process, which makes it easier to find solution.
The discussion on MK802 was installing Ubuntu 12.04 on it, it sure does fits in Linux topic.
Linus Fcuk Nxdia on driver source code is another topic, it DOES falls into kernel level development of Linux, honest, Android was once pulled off main Linux source tree (REF:http://www.h-online.com/open/new ... -kernel-920688.html)
That topic does not falls into the "Android or not" issues....
Provided almost all major mobile OS are a varieties of *nix, iOS is, Windows Mobile is, Android is even WebOS is, but application level, all of them has its own application runtime / structure / design, so it is best to discuss that in their own board..
Anyway, I am not board rules person too, as far as it is not really disturbing, that was just a nice suggestion you may get more support and / or reply on this topic over a more related board, which is the Android board but not the Linux board.