Problems with your ACM SIG Proceedings Copyright Box??

Backup. For the error:

Package caption Error: No float type 'copyrightbox' defined

In case you forgot, the ACM SIG Proceedings Templates are nice looking, but have quite a few quirks. First is this error that you might get:

Package caption Error: No float type 'copyrightbox' defined.

I’m not sure, but I think this is from using the subfig package. In order to “fix” this error while simultaneously getting rid of your copyright box, try

makeatletter let@copyrightspacerelax makeatother

Before the begin{document}.