I just upgraded to SolidWorks 2012 sp1.0 and want to install sp3.0, but my installation manager warns me that

"Additional files are needed based on the products selected."

and that I should enable downloads, but the download option is stuck on the "Install only" setting.

Clearly the download option needs to be "Download and install.", but that's greyed out and I can't select it.

Any ideas?