is the software your using to compile been updated automatically, some of the Unity Demos including the Island demo no longer work with the new version of Unity because when you update the projects, Unity adds another line of code in a script or two which causes the error, maybe a new line of code is added without your knowledge because of an update
also, just read my previous post, wrong choice of words, what i mean is when you got to make a 32 bit app on a 64 bit machine, there may be something that a 64 bit machine does when compiling 32 bit apps, after all, these has to be a reason as to why some programs like iTunes and Switch have 32 bit installers but if you try and install them on a 64 bit machine they reject you telling you that you need to get a 64 bit installer (understandable with iTunes but Switch is a MIDI -> MP3 converter and wasn't made by some big group like Apple)