I do not know what you have broken, If you can not give more information, Screenshots of the error messages and an example file that does not open, then resort to a clean reinstall.
Use the Windows uninstaller to uninstall Gimp.
In C:\Program Files\ delete the GIMP 2 folder.
In C:\Users\"yourname"\AppData\Roaming rename the GIMP folder to GIMP-saved
Download the latest Gimp from http://www.gimp.org
Run the installer.
Edit: Have you considered that it might not be Gimp ? If the files are stored on an external drive or a Cloud Storage service then they might be blocked.
Use the Windows uninstaller to uninstall Gimp.
In C:\Program Files\ delete the GIMP 2 folder.
In C:\Users\"yourname"\AppData\Roaming rename the GIMP folder to GIMP-saved
Download the latest Gimp from http://www.gimp.org
Run the installer.
Edit: Have you considered that it might not be Gimp ? If the files are stored on an external drive or a Cloud Storage service then they might be blocked.