I am using an iMac with El Capitan. OS software is all up to date. I cannot open downloaded apps any longer so I presume installer.app has been corrupted. Can anybody tell me how I can re-install that app?
It has happened twice. Both downloaded from 3rd party. One was from G Technology external drives and the other from ChronoSync
[doublepost=1465068257][/doublepost]Sorry, forgot to add: The error is that a dialogue box opens Verifying 'install.pkg", the disk image bounces and eventually stops. When right clicked says application not responding.
Thank you Richard2 and NoBoMac for your suggestions. It wasn't just the G Tech application that would not open it was also other .pkg files that I had previously downloaded such as Adobe Lightroom, Topaz etc.
On Friday I set up a chat session with Apple Support and over the last three days with help from several of the support Guys the problem has been resolved. I'm not sure which action actually cured the problem but I am now very happy to have a fully functional iMac again. I can't praise the Apple support team highly enough for sticking with me and helping me solve the problem. This is on a 7 year old Mac which is out of guarantee. Very impressed.