Hi Pete,
Thank you for posting your query in Microsoft Community.
As per the description, you are facing issues with apps which are crashing and receiving error code c0000005. I would definitely help you to fix the issue with apps you are facing.
In order to provide you with a quick resolution, please reply to these questions:
1. What is the complete error message?
2. Have you made any changes on the computer prior to the issue?
However, I’m glad to provide you with these methods which will help you to troubleshoot the issue.
Method 1: Download and run the New UI App troubleshooter and check.
**http://download.microsoft.com/download/F/2/4/F24D0C03-4181-4E5B-A23B-5C3A6B5974E3/apps.diagcab**
**Method 2:**You may follow steps from the article mentioned below and check if that works.
What to do if you have problems with an app
**http://windows.microsoft.com/en-us/windows-8/what-troubleshoot-problems-app**
If you need further assistance on any issues related to Windows, please reply and we will be happy to help you.