[Eliminating textures from UV dropdown list]

in the uv/image editor, display the texture you want to remove,
hold shift, then click the X to unlink the image datablock,
in the dropdown browse images, zero will appear in front of the texture
it only works on one texture at a time,
dont display again the texture to be deleted, in the uv/image editor window.
just save, close and reopen
yes it is inconvenient, but for now that seems to be the only way.

[Eliminating textures from UV dropdown list]

hold shift, then hit X,

zero will appear in front of your texture, save your blend file, and reopen and its gone.

[Cannot calculate or upload mesh]

i also have had problems uploading mesh at times, only advice i can give is

only use the sl linden lab viewer for uploading mesh, i've had problems with firestorm viewer not uploading correctly, i have not tried the latest releases of firestorm,

make sure you unwrap your mesh

and also for multi mesh uploads, make sure to rename each uvmap a different name, uvmap1, uvmap2, etc before uploading,

i've had error messages when i try to use the same complicated mesh as my physics shape, but if i use a  simple physics shape with alot less vertices, it seems to upload with no problems, dont know why this happens