Try resetting your Photoshop Preferences
Thanks a lot, it works just fine now. Do you know where this problem might have come from? Should I reset my preferences everytime this (or something similar) happens? Also, as I've reset my preferences, all my works disappeared from the front page (where they used to be displayed). That's not a big deal though.
Adobe Photoshop preferences becoming corrupt is such a common occurrence Adobe has a Startup Shortcut key to reset them and now in CC 2017 there is a preference to reset them.
All versions of Photoshop have bugs. When Photoshop start to misbehave there are three thing you should do to try gett it back in working order. Do them is the sequence. Test after each step and Stop if Photoshop is working.
1.) First check that all you current tools settings are what they should be and the conditions for its use are present.
2.) Reset all Photoshop Tool.
3.) Reset you Photoshop Preferences.
Myself I backup a working set of my preferences and restore those instead of resetting preferences.
There is also the Shift startup shortcut to skip loading optional add on. Add-on and user Action and script can also cause problems... All Problems are not created on the inside of Adobe doors.
Thank you for your quick answer, I take good note of it!
Have a good day