After a failed Photoshop CC update, errors about FastCore, MMXCore, and Multiprocessor plug-ins appear when you open Photoshop. In Photoshop, you can't save as PNG or use Save For Web.
Uninstall Photoshop, delete the Photoshop application folder, and then reinstall.
Third-party plug-ins: Before copying third-party plug-ins from one version of Photoshop to a new version, check the plug-in manufacturer's site to make sure the plug-ins are compatible with the new version of Photoshop. Use the manufacturer's installer to install their plug-ins.
Photoshop-shipped plug-ins: Never copy Photoshop-shipped plug-ins from one version of Photoshop to another; they are not compatible.
For more information about Photoshop's plug-ins, see this TechNote: Downloadable Content (Plug-ins)
Contact Adobe Technical Support by posting to feedback.photoshop.com/photoshop_family, and getting instructions on how to send your installer logs to Adobe.
The log files are located in these folders:
• Windows 32 bit: \Program Files\Common Files\Adobe\Installers
• Windows 64 bit: \Program Files(x86)\Common Files\Adobe\Installers
The log filename includes the product name and install date, followed with ".log.gz." The extension .gz indicates a compressed format.