Unintended Multiple Instances Of A Project Open Everytime I Open Unity

For some time, I've had a Unity project that would always open two instances instead of one, every time I've tried to open it.

One instance won't open if you click it and, if you're using Win 7 Aero, you can see both projects showing the same thing.

Also, a few other observations I've made:

• All instances seem to be rendering in a weird way, even when no camera is on them (for example, objects who would have been destroyed when they exit the camera are staying in the scene for longer than intended)

• After losing and regaining focus on a running game, any input will be ignored while everything else is working perfectly fine.

• I've also managed to open the non-showing instance one, but I'm still not sure how that happened, and from what I could observe, that wouldn't update the other one, the one showing most of the time, but due to the rarity of that, I couldn't make more observations

I hope that's enough info, but if not, I'll try to provide a video too

Thanks in advance

EDIT 1: I also would like to add that my projects are in a Dropbox folder