Well... I have the PS3 version of Dead Island, so there's really only one question I can answer and it's this one:
It's October 15, 2011 at the time of your post. It's been 5 weeks and 4 days since Dead Island was released in NA [Take off 3 days for PAL regions], so I'm going to say... Not long? Possibly since the very first day. Dead Island had and still has many issues on all platforms. Some of them have been resolved through patches but not many...Originally Posted by Sock
I'm going to take a guess and say you already have but...
Have you tried playing in Compatibility Mode [not sure why you would need to but who knows...] or tried to run the Launcher as an Admin?