Why do I get a "Critical Error" error message when I try to generate my report?

You need to install a hotfix. Follow these steps:

Reporter 8.3
Go to Start menu -> FLIR Systems -> ThermaCAM Reporter 8.3 -> Check for updates
This will install Hotfix 2 that solves this issue.

Reporter 8.3 SP1
Go to Start menu -> FLIR Systems -> ThermaCAM Reporter 8.3 -> Check for updates
This will install Hotfix 1 that will solve this issue.