Edit: Sorry, just noticed reply from jfjoubert
Hi Jim,
Please check this and see if you can add X-Plane folder to the AVG exclusions:
https://support.avg.com/SupportArticleView?l=en&urlname=Mac-AVG-AntiVirus-FAQ
"How do I exclude files or folders from scanning in AVG AntiVirus or AVG Internet Security?"
You can specify if you want certain files, folders, or servers to be excluded from AVG scans.
To set up exceptions:
1. Click AVG AntiVirus or AVG Internet Security in your menu bar, then select Preferences... from the context menu.
2. Select the Exceptions tab.
3. Click a shield in the left panel to select it.
4. Click the lock in the bottom-left corner of the window, enter your system administrator credentials, and click OK to grant permission for the changes.
5. Click the + (plus) symbol to add a file, folder, or server to the exceptions list.
6. Navigate to the file or folder you want to exclude and click Open, or enter a server name and select the relevant service from the expandable menu, then click Add.
Your exception is now configured. To remove an exception, select an item to highlight it, then click the - (minus) symbol.