Wrong number of monitors

I love this extension, but I'm having one pretty big problem with it: "Sidewise currently believes you have 6 monitors connected to your system." I have only three. I've tried to get it to detect again, uninstalled/reinstalled Chrome/Sidewise, adjusted resolution and nothing changes it.

This wouldn't be that big a deal, except any time I click on something that opens a new browser window, it opens in one of my non-existent displays. I then have to go to Chrome on the task bar, mouse over the new window, shift-right-click> move to manually get it back on a real display.

If anyone could help with this I would be very grateful. This extension is exactly what I've been looking for for quite a while, and this is the only real complaint I have with it.