I am having really a lot of trouble trying to get this to work. Not sure what settings to use.  i setup the shared folder correctly and i can access from my iPhone explorer app  and other windows PC. 
I did get it to work with the same setting but sometimes it doesn't work. very weird.  I also noticed the Workgroup doesn't matter, it works with or without it.   The weird part is that it works intermittently. 
I also have a DIR-855L router and I turned on the setting "NetBIOS announcement".   Anyone here got this to work? 
