Sadly, I am not able to get the plug-in to load on any 5.4.2 project. Doesn't matter if it is a brand new project or a project converted from a prior version (replacing the existing HammUEr plugin). Love HammUEr, BTW. Brilliant!
I concur with SurlyBird, it appears 5.4.2 does not load the module for the 5.4.1 plugin, and throws an error on launch / creation of a project. Might you be able to update for 5.4.2?