Video stops working and import locks up, or the following error occurs: "Adobe QT32 Server.exe - System Error. The program can't start because [filename].dll is missing from your computer. Try reinstalling the program to fix this problem."
In your Norton Security History, the below .dll files are listed with (Suspecious.Cloud.7.F.) next to the name.
Make sure you're running the most recent version of your anti-virus software.
Add the following files to your un-quarantine list in Norton:
When Norton Anti-Virus is on at the time you install Lightroom 4, these files are added to the quarantine list. These files relate to video files, so when they are quarantined, you cannot import video files.
For more information about general troubleshooting for video files, see TechNote: Troubleshoot video issues in Lightroom 4