Thank Peter.
It seems this error happens when the default base pixel size to generate the overviews is too small. For this reason, I am thinking to create the image service using the New Image Service Wizard as usually but now, making sure the default "generate overviews" and "compile the service for publishing" options are unchecked. Finally, create the overview using a bigger base pixel size.
I haven't told you that the warning message that I got when I was trying to see the service in full extent was:
Warning: maximum number of rasters selected for the requested AOI. Number of selecter raster exceeds the maximum rasters allowed.
What I think is that I have to edit the Max. rasters displayed parameter in the Image Service properties, then compile it and finally restart the image service that I had published.
What do you think?
Ximena C