OS X mavericks update issue am trying to update my iMac 21.5 inch mid 2010 from os x mavericks 10.9.1 to 10.9.5 to work on Xcode 6 but it always fail and give me the alert message OS X Update could not be verified . It may have been corrupted or tampered with during downloading . Click download and check the update again

can anybody help
If you're running antivirus software, you may wish to try disabling it and downloading your updates from the App Store again. If that doesn't work, try downloading the combo update from here:

http://support.apple.com/kb/DL1760

You may find that this works where downloading from the App Store fails.