Q: Applications won't work? PowerPC Applications not supported?

PPC apps were last supported in 10.6.8 for install and 10.7.0 for legacy use meaning you could use them but no longer install, when 10.8 came out they were done.

Your system originally shipped with 10.7.3 so theoretically it could be downgraded through an install on a clean partition or external drive or wiping your current HD but again, you can't install PPC, just run it if it was installed AFAIK. 

What is your OS version?

Do you have any external drive connected which may have older versions of those applications?

I had this same problem. All of the sudden every single app in 'Applications' was showed the '.app' extension and would not open, saying they were PowerPC apps. Obviously that was not the case. Numbers crashed, Mail quit behaving normally and would not send or receive mail. What could have caused this issue? I restarted and it is behaving normally now, but it was a pretty scary moment there for a minute.

bdockery wrote:

 

Every time I try to open an application (even Apple applications like iTunes, iBooks, or Contacts) it gives me a message "You can't open the application because PowerPC applications are no longer supported."

 

I have El Capitan Version 10.11.1. I have a Mackbook Pro (15-inch, mid 2012)

 

How do I fix this?

Try restarting your computer.

In the past, did you move your applications out of the Applications folder? Have you tried opening the applications directly from your Applications folder instead of using the Dock

First question no. Second question yes. MacBook Pro (Retina, 15-inch, Mid 2015). 10.11.5. Bought earlier this year.

Did you try booting in Safe Mode as suggested?

As I mentioned, I restarted and the problem went away. My concern is what could have caused the problem? I use my personal computer for work so I have company forced security software install (Webroot SecureAnywhere). I don't really trust it after it came up with '.plist' files it said were infected, so obviously that could have caused the problem, but are there any other theories?

I am not familiar with Webroot SecureAnywhere but it a well known fact that antivirus software on the Mac are the cause of much more harm than good.

bullockrm wrote:

 

As I mentioned, I restarted and the problem went away.

Sorry I missed the green Solved.

As you know the OS is complicated literally 100,000 I/O, glitches happen periodically. If it was not solved that would be a different issue.

I would not lose any sleep over it.

Sorry I missed the green Solved.

That would be because it isn't marked as solved.