It's hardly unheard of for a Mac to pick up weird issues. My wife's Macbook has a thing where the mouse cursor will just disappear when she wakes the thing up from sleep. Poking around on the internet finds other people with the same problem and no good solution (zapping PRAM doesn't help, neither did a full OS reinstall). It's just a live with it affair. The only fix is to close the lid and open it again, which isn't too bad but the issue crops up multiple times in a day and is quite annoying.

I manage a bunch of Ubuntu desktops at work and the most common issue seems to be that if you leave a machine alone for too long (a week or two), then when you log back in the DBUS or something seems to get hung up and the whole interface is mostly unusable until you log out and log back in. It can be so bad you can't even focus a window anymore or change the input focus. Next most common issue is DKMS randomly fucking up and installing a kernel without the nVidia or VirtualBox modules leaving the machine useless.