Trying to access my Mac from a Windows 7 computer, I fail with the infamous error 86 incorrect password.

Now this appears to be a well-known problem with countless threads on the internet giving as many "solutions" as there are discussion threads about it (mostly ranging from installing third-party commercial samba servers, to switching to some other protocol, to compiling a plain-vanilla Samba installation - the latter which I will probably do when I give up this :) )

I am stubborn, and I believe there must be some problem here that can be solved or worked around, but there is surprisingly little detail about this problem. It appears to have something to do with a mismatch of authentication methods. Trying to run samba in debug mode:

sudo /usr/sbin/smbd -debug -stdout

gets me this output when trying to access it from Win 7

...
smb1_dispatch_one [smb_dispatch.cpp:377] dispatching SMB_COM_SESSION_SETUP_ANDX
smb1_dispatch_session_setup [session_setup.cpp:261] FIXME erase existing sessions
log_gss_error [gssapi_mechanism.cpp:97] gssapi: gss-code:  Miscellaneous failure (see text)
log_gss_error [gssapi_mechanism.cpp:113] gssapi: mech-code: unknown mech-code 22 for mech unknown

What is the problem here, and how do I fix it?