Blender: "Include skin weights" greyed out on the previewer. Possibly the vertex groups?

[Chriss Daysleeper]

So - I made some pants, then I parented them to the armature with the armature deform option. I then weight painted them manually, and I think everything turned out great. When I went to export the Collada, I made sure to check the "Second Life Rigged" preset as well. Basically, I think I've done everything correctly.

The problem is that when I upload them onto the previewer, the Include skin weights button is greyed out. I spent quite a while trying to figure out the problem. I eventually decided to check my old mesh top I did a while ago, and the only difference I could find was that the mesh had all the vertex parts in it's group, while my newer pants only have four, those being the two Knee and Pelvis parts.

Do you think this could be the problem? If so, how can I fix this and avoid it in the future. It's been a while since I've tried mesh, so I think I've forgotten some minor things. I'd hate to have to add them all in manually, if there's a way I can copy vertex groups, then I'd be set.

[Gaia Clary]

pprobably you have not all necessary bones defined in your rig ? Yuo can check here for possible errors and fixes:

http://blog.machinimatrix.org/upload-issues-with-rigged-meshes/