The algorithm (Spatial API) used to do the conversion is not able to handle much more than 2000. The limit has been moved up to 4000 in V10, but it doesn't take much of a mesh to exceed even 4000 vertices. You will need to use the "Stitch" tool. When the "Stitch" tool is selected. Note the Option button in the Data window.
This limit has nothing to do with converting solids to surfaces, 2000 surfaces on a solid would be very unusual.