Can't connect iPad to Samba/network shares

Greetings all-- We're running several network shares on our systems which I'd like to access from our iPads. I've tested the samba shares on multiple PC's and Macs, and can log in no trouble. On the iPad, I've downloaded two network file browsers, FileExplorer and FileBrowser, and when I try and log in with either, I get "access denied." Would there be something specific the iPad that would be blocked by the server itself?

Thanks!
Jeff