Attached Link: http://www.jmadden.info/WindowsHelp3.htm

Yeah, I was hoping it was some kind of quirky icon problem since you didn't mention whether app launching was working or not. You might try whichever of the two methods listed in this link you may not have tried to fix the association. Beyond that, it's going to be either reinstall time or edit the registry key directly to set the association. Since Acadia's experence seems very specific, it seems more likely to me that your's is somehow related. You might try reinstalling the service pack.

"Democracy is a pathetic belief in the collective wisdom of individual ignorance." - H. L. Mencken