Slim syntax highlighter causes file opening to hang

If I have the Slim and Slim Ruby Support plugins installed (as they are by default), whenever I try to open a file (either a .rb file or the Gemfile), RubyMine hangs showing a "Loading..." screen. I checked the idea.log and found a bunch of exceptions that seemed to be triggered by:

java.lang.NoClassDefFoundError: Could not initialize class org.jetbrains.plugins.slim.RubySlimSyntaxHighlighter

Reinstalling RubyMine didn't solve the issue, but deactivating the Slim and Slim Ruby Support plugins did.