Not able to set custom shortcut for increase/decrease brush size in Photoshop CC 2014 on Win 8

Question

I am using Windows 8 and PS CC2014 and the issue is that I can't assign custom shortcut to the dot. I have been using , and . as decreasing and increasing brush size and it has worked well in every photoshop, even cc2014 in win7 but not in win8 it seems. It lets me to change the , and just tells me that it is in use in somewhere else but i can still change it. But I can't do the same with . as it complains it being used by an application although I have cleared that from the original place and left it empty, photoshop still recognizes it if I press it although it would be empty but I can't assign that key to anything else either.
Small thing but drives me crazy as I had to assign it to another keys and I am using the shortcuts from muscle memory mostly and end up changing the brush when I had an intention to increase the size. I tried to google this but couldn't find anything similar solution.

Answer 1

I didn't manage to get it to work :c Restart won't do anything and I tried to reset the preferences by deleting manually the file with keyboard shortcuts. I managed to get them to the factory settings but that was about it. Everytime I try to assign "." to somewhere (including to the place where it already is), it gives the red x and says "the shortcut is not valid. It is being used by another application." (not sure what it is in english exactly, I happen to have my PS in finnish unfortunately ). Plugin disabled mode did nothing either.
I have changed that shortcut many times to different versions earlier and this is first time I see that message or am not being able to change the shortcut. And I installed the photoshop yesterday from fresh and first thing I did was making the shortcuts and it gave the error from the first use.