Well, like you said, two weeks was normal, now it's not, obviously something happened at that time. Some problem is with the intersect, or in another game that you play could have caused that. Especially if you have a shared computer (small siblings, minor nephews, etc). What I advise is you keep an open mind.
If you are working on a project and everything is fine, you are making progress, keep it up, maybe it's just on your computer, in others it might be normal. And by the resolutions presented are the most used by players in general, I particularly do not give up 800x600 for nothing.
Keep working and do not let this relatively small problem get in the way of your project. Who knows in the future maybe it will solve itself as it came.
If you need someone to test your project, I volunteer to check if everything is okay. But compared to so many other errors that are here on the site that people show, this is not so great, it really can only be technical problems.