samba - Feb 2005 - Samba share mapped to a virtual directory via UNC within IIS doesn't work

I have a Samba share that I've created from a Linux box.  I've mapped
this sucessfully to drive in Windows 2003 server.  I'm also able to
read/write to it under Windows explorer just fine.  It's using user
security so I have to enter the username and password defined in the
Linux box when connecting to this share.

I then mapped a virtual directory under IIS to the UNC name of this
Samba network share (\\MachineName\ShareFolder) and saved the Samba
connection login.

This is when the problems began.  Now whenever I goto my browser and
type the url to that folder I get an error 500.  The IIS log file
shows this:

2005-02-03 14:29:11 192.168.1.150 GET /test/test.jpg - 81 -
192.168.1.150
Mozilla/4.0+(compatible;+MSIE+6.0;+Windows+NT+5.2;+.NET+CLR+1.1.4322)
- 500 16 1326 15

"/test/" is the virtual directory that I've mapped the Samba share
to.

Is this caused by a permissions problem?  I don't see any other reason
for it.  I'm not accessing a script, just a static file.