Sure. My system has "Playlists" too, which contain both playlists and smartlists. Playlists work fine, smartlists don't.
When I try to access smartlists on the roku, I get the "waiting for reply... (EXIT to cancel)" screen. Then nothing for a couple of minutes, followed by the "Failed to load browse data. Invalid results received" screen.
On the upnp server log, I get the following:
01/06/08 08:51:29 - Browse BrowseDirectChildren 0()
01/06/08 08:51:34 - Browse BrowseDirectChildren 4(Playlists)
01/06/08 08:51:36 - Browse BrowseDirectChildren 69(Playlists\Smartlists)
On a very odd occasion, the smartlists will actually work (maybe one time in twenty), so I'm guessing it is a timeout issue, but when it does work the reply is almost instant. I don't have a huge amount of smartlists, just the defaults plus a few. My network isn't clogged, and the roku+media centre combo works flawlessly otherwise.
Another thing to note is that when is DOES occasionally work, I can ALWAYS then play the chosen smartlist without a problem. The issue is ONLY with browsing smartlists to begin with.
I hope that helps. Thanks.