I am having the same problem on an old WordPress install (3.7 maybe?). It’s happening when I try to update both plugins and WP Core.
Akismet is also failing to find the server too.
I am the host here and haven’t changed anything apart from possibly my OpenSSL version.
If the theme you’re uploading is bigger that the PHP upload limit, it will throw this error (rather than a more helpful “too large” error). Try uploading the theme manually or via cPanel if you have it.
