[eluser]BrianDHall[/eluser]
A couple of things don't make since to me here. For one, CI is looking for a system file in the wrong place - in fact, a place that makes no sense at all.
It is looking for ./system/libraries/Exceptions.php relative to /media/disk/websites/usability/httpdocs/system/codeigniter/Common.php - if it was looking for ../system that would work, but of course there is no system/codeigniter/system folder.
The other thing is perhaps this is just an IDE issue, but my line 127 is "if ($is_subclass == TRUE)", not a call to require.
Putting that aside, the problem seems to be that either your APPPATH or BASEPATH is simply wrong, you are likely just missing a dot. This is defined in index.php, so along with wabu this is likely where the problem is.
Remember, ./ means "same directory as this file", ../ "start at one level above this directory".
If that isn't it then I can only conclude you over-rode some core function that is causing this problem.