We merged some pull requests earlier today, one of which didn't have parentheses where it should have so we put those in right before publishing the plugin. Those were on line 308 of disqus.php and were most likely the culprit for this error. It looks like this error affected less than a handful of people.
If you were using the trunk version of the plugin (you'd know if you were) you'll want to reinstall the plugin as you may not have truly updated to the latest version.
If you weren't using the trunk version of the plugin, somehow you were able to download the penultimate version of the plugin right before we published the final version. Reinstalling the plugin should solve the issue for you as well.
Sorry about this hassle, let us know what you find. Best,