For TheChair:
The direct link to the free version of Malwarebytes (where you could disable the trial of the 'Premium' version) has been removed from the company's website. You now have to download and install a 14-day 'Premium' trial, which will revert to the free version once the trial has ended.
For Hans:
Open Malwarebytes and check on the version number. (NB: That's not the version number of the database but of the program itself. You'll probably find it across the very top of the window).
There was a known problem with version 3.0.5, with constant messages appearing about Real Time Protection Layers being turned off, that was meant to be fixed in version 3.0.6. [The current download appears to be for v3.0.6.1469]. So, if you happen to have been one of the last people to install v3.0.5, simply uninstalling it and then downloading the later version might do the trick.
However Malwarebytes also have another product, called AdwCleaner, which is completely free and seems to do the same job as the free version of their Anti-Malware program anyway. So you could try that instead:
https://www.malwarebytes.com/adwcleaner/