Connect Ubuntu 11.04 to xbox 360

The XBMC FAQ contains some info on setups that are supposed to work:

http://wiki.xbmc.org/index.php?title=UPnP_Sharing

I haven't used ushare so can't comment, but for one I have used and I know works well, try installing Serviio on your server - it's quick and simple. If this doesn't work then there's something up elsewhere (firewall on Linux box?)

Serviio - free DLNA media server

Serviio is a free DLNA media server. It allows you to stream your media files (music, video or images) to any DLNA-certified renderer device (e.g. a TV set, Bluray player, games console) on your home network.

Serviio works with any DLNA compliant device (TV, Playstation 3, etc.) and some other (XBox 360). It supports profiles for particular devices so that it can be tuned to maximise the device's potential and/or minimize lack of media format playback support (via transcoding).

http://www.serviio.org/