from here you will find the straight solution for after Double click on folder and application can’t open, forward music in iTunes not working correctly. most of the Mac and windows users alway keep mouse arrow moment/ Speed and Double Click or Single click to be set on maximum speed. in this case you made wrong setting of your system. one of them is occurring in this case. Double click not woking on folder and file for open it, So you have to do right click on it and tap on Open option. i also face this problem many times but it has been automatically resolved when update OS X or downgrade OS. So don’t be panic here is the complete solution for fix double click not working after OS X update. but without Update OS X here is the solved solution.
This solution is working in OS X Yosemite, Mavericks and Lion.
Steps for Double click on folder and application not working (Solved)
Step 2: Now click on System preference,
Don’t close Accessibility setting folder try out by open any folder with double click on it.
In a single path you have to move System preference > Accessibility > Mouse & Track Pad > Double click. for Slow down Double click on folder.
Also useful: Optimise/ improve battery life of MacBook Pro and Air.
Sound is good right! that’s enough for short Double click on folder not working, when you try on MacBook Air, MacBook pro, MacBook pro retina with track pad or External USB mouse.