On what computer operating system is your Premiere Elements 12 running? I will assume Windows 7, 8, or 8.1 64 bit for now.
Do not bother with Repair.
Please uninstall Premiere Elements 12 and QuickTime latest version.
Do the free ccleaner run through to get rid of leftovers from incomplete uninstalls reinstalls
With antivirus and firewall(s) disabled, reinstall QuickTIme first and then Premiere Elements 12 to the default location on the Local Disk C.
Once 12 is installed successfully, then install the 12.1 Update using an opened project's Help Menu/Updates.
We will be watching for your results.
That was the first QTCF.dll issue that I remember seeing. Glad the suggested troubleshooting worked for you. You did a great job following through on the troubleshooting to gain your success.
Best wishes with your projects. Please do not hesitate to ask if you have any questions or need clarification on your Premiere Elements workflows. We always appreciate the opportunity to be of assistance.
One small point: the official documentation built into Premier suggested loading QT after loading Premier. You may want to verify latest releases either (1) have the user install QT first, or (2) warn them to install QT first before Premier, or install it for them.
Thanks for the comments and suggestions.
I have always installed Premiere Elements versions with the latest version of QuickTime already installed.
So I will look into the Adobe documentation on this versus the actual effect of QuickTime/Premiere Elements installation order.
I am not Adobe so I do not have access to its technical writing staff. But we will seek to clarify on this and spread the word.