I've had the same issues twice.
I can't recall what solved it the first time, but the last time the problem dissapeared after I installed the newly purchased The Grand.
By the way: it wasn't only in the inspector, but also in the mixconsole and the 'edit track settings' window (well, actually all over Cubase). You will notice that, when you change tab and then click inside the tab window, it will change over.
I also noticed that, when it occurred in C8, it was also happening in C7.5.
So i'm guessing something got messed up when installing C8 that was resolved by installing The Grand.
Since, for as far as I know, the only thing they have in common is the eLicenser, you might try to re-install the latest elincenser software.
I have sent an official support request a while ago (before new year) with a screenrecording of what is happening, but I haven't heard from them yet. Luckily enough it got sorted out by installing The Grand 3. Otherwise I still wouldn't be able to work with it.