We've had issues with that also. One thing to remember that if the (can't remember which right now) sysval on the as/400 is set to non-case sensitive, you'll need to key in you password in either all upper case, or all lower case (forget normal logon rules). You also may need to change the setting in iseries navigator so it won't use the Windows username and password "no prompting" - to just the user name, and save the password when you create the map.
We used iseries shares for years...then along comes XP. Gee thanks. I really want to move everyone to Linux, but that's neither here nor there. What I've done is...
If we are getting a file to the ifs, usually from a cpytopcd, I add an ftp to the program to copy to a windows share they already have. If you'd like to use that, I can post some code for you.
Mark
SELECT * FROM management WHERE clue > 1
> 0 rows returned
--ThinkGeek T-Shrit