‘You can only have one Club Penguin window open at a time’ triggers when other Houdini-based CPPS’s are open

[noahball]

So let’s say I’m playing a CPPS such as https://cozypenguin.net
I decide to go and have a play of CPBack, as soon as the game loads I get an error telling me that I can only have one window open at a time. This makes sense, but having this trigger with other Houdini-based CPPS’s is annoying.