I am working with stage 1.6.2 on player 1.6.4.
I am trying to work with the blobfinder interface and
although the blobs are seems to be recognized
correctly and the color, x, y, etc. are set to
expectable values, the range is always set to 0.

I tracked the problem to the the function
blobfinder_update at the file model_blobfinder.c and
found the location where blob.range is set.

Can anyone help here?
What am I missing anything?

I'm don't have the code in front of me, but if the Stage model is calculating and storing a range value OK, then I'll guess that the value is not being passed to player in the plugin code. Check <stage>/src/stg_driver.cc, in a method called something like:

void StgDriver::RefreshDataBlobfinder( device_record_t* device )

This could easily have been overlooked, because most people choose not to use that field because no camera system provides that kind of data. I put it in there because it's sort of like a stereo camera, I already had the data computed, and I used it once or twice. 

You should be easily able to add the range field to the player packet.  I'll check to make sure this is working in CVS HEAD before I release another version.