Hmmmm … I just noticed that my VST host no longer passes mouse events properly to the plugins.
After scouring my code for a few hours I compiled the juce demo VST host and found that it has the same issue. Oddly, the prebuilt does not though (guessing that the prebuilt may not be using the tip though, so this make sense, since this is a new issue).
The plugins I am using are AU … probably carbon … so I am guessing that it is an issue in the carbon wrapper. Whatever the case, it definitely passed the mouse clicks as late as a couple months ago, but does not currently.