a bug in my mouse

Just started getting this bug in my mouse. The left-click function won't work on the top menu bar in pretty much any application, on any desktop. I am able to access functions sometimes only by using the tab and shift-tab to move back and forth through menus, etc.; but this doesn't work in all programs. Notably, I can't click on the home icon in any browser, nor can I use any menu functions. When I try to right-click, part of my screen (more or less the upper left hand corner, about one quarter of my screen) acts like I am on the desktop rather than in a program, and I see the menu functions to configure desktop. I've seen this bug before, and it seems to go away after weeks of annoying me, or I reinstall everything and then (if I recall) it seems to go away, but I don't want to reinstall everything over what I think is just a bug. Is there perhaps a config file buried somewhere that will fix this bug? Or has anybody else ever had a similar problem? By the way, it all seemed to start after I used smplayer, on recommendation from another user here. (Not blaming anybody, as I have totally messed up then rebuilt my machine many times, often just after trying out some new program.) I prefer vlc, but that, too, has been buggy and always crashes, and smplayer works pretty well. I remember making changes in the smplayer config (but nothing that I thought would affect the mouse); although it seems that thereafter is when I started having these problems. I've gone through the smplayer settings again and again, and don't find anything that ought to affect the mouse. Please help, if you have any clue what is the cause of this bug. Thanks. Bill