Symptoms
An error is thrown with the message: A generic error occurred in GDI+. and Page URL:/MS9101c/admin/EntityProductImageMgr.aspx when attempting to Update the Multi-Image Manager.
Cause
The AppConfig: MultiColorMakesSwatchAndMap is set to true and the product variant contains Color attributes. The software is attempting to save the Swatch but the ~/images/product/swatch folder does not exist.
Solution
Create the ~/images/product/swatch folder and attempt the Update again if you intended to create a Swatch, or set the AppConfig: MultiColorMakesSwatchAndMap to false.