Q: Mac OS X 10.9 cannot double-click to open app  . please help me !

Hi Kun Nguyen,

Welcome to the Support Communities!

Did you restart your computer after installing the Mavericks upgrade?

Are you using the trackpad or a mouse?

You should be able to click once on an app icon on the Dock or in Lauchpad.

The only time you need to double click is if you are opening the app from the Applications folder in Finder.

If restarting the computer doesn't resolve your issue, try these steps ...

Portables and Magic Trackpad: Jumpy or erratic trackpad operation

http://support.apple.com/kb/TS1449

Intel-based Macs: Resetting the System Management Controller (SMC)

http://support.apple.com/kb/HT3964

OS X Mavericks: Reset your computer’s PRAM

http://support.apple.com/kb/ph14222

Cheers,

- Judy