I'm going to ask the first question anyone probably will ask you: have you tried updating your drivers? Every time I've had a problem graphics related, it's usually helped me to get the latest drivers. Probably not a solution, but most likely a good start
Yup, got the latest drivers and all. Actually, it's kinda funny, but it resolved itself... After switching to extended desktop again and playing with my tablet I found out the tablet works normally, and after using the tablet for a while the mouse stopped teleporting around my screen by itself. I dunno why, but I'll accept…