After the latest race 07 update this was a huge problem for me and others from what i had read in other forums/websites..
The only way that can fix this issue for uploading and downloading SETUPS is as follows:
Uninstall all the games and steam, do a registery clean. BUT PLEASE DO NOT DELETE SIMBIN FOLDER FROM MY DOCUMENTS.(if needed, do a copy of this folder and paste to desktop for keepsafe, You can always do a copy and paste back into my documents if need be)
Restart your pc
Reinstall steam
Reinstall games
after this is done then you should beable to reupload and download setups..
I had this issue and was solved after doing the above. In that order