There is a known issue with TechSmith Relay Recorder with Divx 8. If Divx 8 is installed, Camtasia Relay will appear to capture the screen but when the recording is stopped, the software immediately quits.
Attached is a fix for this issue. Please download the attachment to the machine with Divx 8 installed and then delete the txt file extension (filename Fix DirectShow AVI source filter.reg). Then double click on the file to apply the registry change.
This issue is resolved in Camtasia Relay Recorder 4.2.0 or later.