One week ago my pc downloaded a file with no authorization, so I had to run my antiviruses. In particular, I installed malwarebytes and it reported 13 threats that are now in quarantine. Since then, I had no other issues: i run many and many times my antiviruses (malwarebytes, windows defender and avast) and nothing bad was found after the first day. So I dont think its a malware issue (it's one week now and nothing strange still happened to me). The only thing that changed is my old game Port Royale 2. I've been playing it with no problems until last week. Now, when I start it, the trailer starts but right after it, the main menu gets freezed, and then the app crashes with this message: "The thread tried to read from or write to a virtual address for which it does not have the appropriate access." Now, since its the first time I get this message, I guess it is something related to malwarebytes or to some sort of malware that is somehow still going on. Any suggest?

I think it's just a problem if you installed it in program files. Try installing into a different folder name
Also try admin mode

I've tried the admin mode but nothing happened. So you say I should reinstall the game in another folder? But why did it start having problems only after I installed Malwarebytes?

I don't think it's malwarebytes fault. Could have been an update to windows that did this. Also you didn't say if you had it installed in program files.
There are usually access problems if it is installed in program files

The game is installed in D:\Program Files (x86). It's the default installing folder of this game, and it's where it has always been installed.

Anti-virus and anti-mallware software does scan active processes and open files at times, and some games may dislike that kind of behavior. I'm not pointing any fingers here, just saying that it's certainly possible.

I have not used Malwarebytes in ages, so I'm not sure on this one. Usually you have the option to add an exception for the game's executable maybe, so it's skipped during scans. I know the game. It's a personal favorite :).

Any solution?

That sounds like some memory access protection kicking in. Not necessarily, as a quick search reveals various other possible reasons for such an error, including wrong RAM timings/speed or other software conflicts, but in your case it does seem likely, if it started after installing some new security software. And it can block such access, for example this is from HIPS logs for Comodo Firewall in my case, while playing Diggles. It doesn't cause any problems, but maybe in case of PR2 it does. May want to check and see if Malwarebytes has such logs to see if it lists blocking anything for it, and like WinterSnowfall said, add it to exceptions from any active protection.

See if disabling Malwarebytes temporarily solves the issue. If it does, try to add an exception for the Port Royale 2 .exe file, as I said before.

Guys I did everything you said but nothing changed. I even uninstalled malwarebytes and the game iself, reinstalling it in another folder. But still nothing happens. Seems to be nothing related to malwarebytes, folders or corrupted files (since I reinstalled it a couple of times but nothing changed). What else could it be?