When i choose to Upload to my Arduino board it says:
BUILD FOLDER DISAPPEARED OR COULD NOT BE WRITTEN
not sure why this is.
Which platform are you using (e.g. Linux or Windows, etc.)? Do you have permissions on the folder?
mac osx....how do i obtain permission?
mac osx....how do i obtain permission?
Ask Steve Jobs. 
Lefty
If Steve is too busy, you need to see if you as a user has permission to write to wherever your Arduino sketch software was installed.
Either you as a user has to have permission, or possibly a group permission, or maybe you have to change the folder to allow you as a use to access it.
I'm on linux, so don't know the OSX details.
Somehow you have to temporarily elevate your credentials, or become root, change things, then go back to regular user status.
Or, maybe it just didn't fully install.
http://www.arduino.cc/en/Guide/Troubleshooting
Second question / answer.