Avastar keeps giving problems to me, but I am quite stubborn and would like to solve what's wrong. Today,  using the instructions of Eleanora Nevell , I tried again,
here they are up to point four:

[23:00] Eleanora Newell: Workflow for unweighted mesh:

1.  Have your mesh and the avastar figure and rig (I like them on different layers,

 you can put them as you like) ready.

2.  Select your mesh and the rig.  In the skinning panel, choose weights from bones 

(or meshes if you want them from the avastar figure meshes - the figure must be visible

 if this is your option).

3.  Press the fitted mesh configuration and apply.

4.  Fitted mesh panel in the Bone Presets Operator panel at the bottom of the toolbar, 

weight should be set to Move and Generate Weights checkmarked.

No "generate weights " appeared, then I made it to have it, don't ask me how, no idea, 

but no checkmark, then I closed everything again and opened an old file, so when I tried to 

move weights I got an error message, here it is.

Here I am. Waiting.

 And trying again, now the mesh seemps properly rigged with weights. I will let you know more

 X mirror does not seem to work

But finally I made it to weight the mesh, which is great. 

 ok, fearing it will not export to dae I check the weights, and get  this, more

 than 700 etc verts with more than 4 weights, but..

when I check one weight, I get a lot of 0 on many different parts. How was that possible?
I did not add weights, so Avastar did it, or I used it in the wrong way. As I thought, it is not possible to create a Dae file