想买trine2但是当按下buy app的时候， 提示
It may be damaged or was not signed
但是购买其他则没问题。
然后搜到了一个答案，
I had the same problem on a MacBook Air that ships with Lion
This is how you fix it
Close Every App (Safari, iTunes, AppStore, etc)
Launch Finder
Press CMD+SHIFT+G (or click on Go then Go To Folder)
Type the following /var/folders
Open up Console (Spotlight Console and launch it)
Open The AppStore
Try to buy something free and you will see this message "The product distribution file could not be verified. It may be damaged or was not signed."
Switch to Console and look at the error message
然后我查看log， 发现是yy这个文件夹， 删除即可
FRPurchaseManager: Preflight operation for 483381002 failed with error: Error Domain=com.apple.appstore Code=0 "The product distribution file could not be verified. It may be damaged or was not signed." UserInfo=0x7f8093a8ccb0 {NSUnderlyingError=0x7f80958129a0 "The requested URL was not found on this server.", NSLocalizedFailureReason=Cannot create PKProduct from "file://localhost/var/folders/yy/34ybh2150q7bttr7zygr_jn00000gn/C/com.apple.appstore/483381002/preflight.pfpkg" Error Domain=NSURLErrorDomain Code=-1100 "The requested URL was not found on this server." UserInfo=0x7f80958bbac0 {NSUnderlyingError=0x7f8095e0ba40 "The requested URL was not found on this server.", NSErrorFailingURLStringKey=file:///var/folders/yy/34ybh2150q7bttr7zygr_jn00000gn/C/com.apple.appstore/483381002/preflight.pfpkg/index.sproduct, NSErrorFailingURLKey=file:///var/folders/yy/34ybh2150q7bttr7zygr_jn00000gn/C/com.apple.appstore/483381002/preflight.pfpkg/index.sproduct, NSLocalizedDescription=The requested URL was not found on this server.}, NSLocalizedDescription=The product distribution file could not be verified. It may be damaged or was not signed.}