The coatl scripting engine has encountered an unrecoverable error and will be restated. Please run Live-Update."
The message doesn't say just that. It also asks if you want to open the error log to see the error details, which is what you should have done, since the details are what we need to know about the problem.
Also, the default error log might not be detailed enough so, before the error, be sure you have Logging enabled in the Troubleshooting section of the GSX Settings Page. If you don't have it, check the box and Restart Couatl. Then reproduce the error and, when the error comes out, exit the sim and check this file:
%APPDATA%\Virtuali\Couatl.LOG
ZIP the file and Attach it to a post.
It's important you reply NO to the request to restart Couatl when asked because, if you allow to restart it, a new LOG will be created, overwriting the one with the information about the error which we need to check.