The site was a simple enough copy along with a backup and restore of the MySQL database. However when I came to run the website I got the message "Error loading MacroEngine Script (file:...)"
After a bit of digging I found two useful things; one to help with debugging and another to address the actual issue mentioned above.
Assist with debugging
Within Ummbraco (prior to version 7 I believe) if you want to debug any issues you can update the following line within the web.config:
Once you have done this you can visit your problematic page with the following URL parameter on the end "?umbDebugShowTrace=true" and it will output trace information that may highlight any issues:
The issue that it actually highlighted was "There is no Lucene index in the folder..."
Fixing the issue
No after a little more digging this was simply resolved by going in to the App_Data folder within my site and emptying out all the folders within "TEMP/ExamineIndexes". So I was left with the following empty folders beneath ExamineIndexes:
