Infinite SEO stylesheet error

Hi. I just updated Infinite SEO, and now when attempting to access the sitemap, I get the following error.

Error loading stylesheet: An unknown error has occurred (805303f4)

I have tried disabling all plugins, and re-enabling only Infinite SEO by itself, with the same results.

Interestingly, there is no error if I disable the stylesheet in the plugin’s settings.

I was thinking that it may have something to do with SSL, but get the same results with and without https://

Any ideas?