samba - Mar 2009 - any experience with MS SQL Reporting Service to Linux based Samba share?

We have several customers who have sftp access to a dir on our CentOS 
5.2 server. They push data to us using ExpanDrive - sftp as a windows 
drive. Works very well.

We have a need to push data back to them from MS SQL Reporting Service 
so we've set up a 'master' user and made it a member of each of the 
customer's private group, and set group write permissions accordingly. 
This all works as expected: we can map to the customers samba-share from 
our windows boxes and write all manner of data using Windows Explorer 
and other tools (editors and such.)

It really couldn't work much better.

Except that when we try to connect SQL Reporting Service directly to the 
customer's share using the master user credentials, we get an Access 
Denied error. It seems that SQL is doing something differently than the 
rest.

Has anyone experienced this or similar problems?

Thanks!

    Bo