The plugin interface has a weird font, it’s gibberish!

If your Animation Composer plug-in interface looks this:

It looks like you have somehow corrupted the Lucida Grande font. Probably you have multiple version of this font installed.
Please, open the Font Book application and check whether there is no yellow exclamation mark sign next to the Lucida Grande font.

Here’s a screenshot in which you can see how it should look like when there are no issues with that font.