Similar problem here: UV-mapping a texture to a cube works fine but when I export to Collada and import it back in Blender the texture is gone. Using Blender 2.63. Any help is greatly appreciated.
Check how many textures your material has defined ( There might be a pre-defined texture called “Tex” at the very top of the textures list, with no icon ). If you define the texture for it, and remove all other textures from the material, the exporter should be able to handle it.
I’m still looking for a way to export multiple textures though. Anyone?
Found the culprit: I was using a more recent Blender build rather than the stable release.