I have moved the materials database to another partition of the same disk of my PC containing all my solidworks parameters. This is to facilitate sharing between machines.
I'm not sure if it's related but when I assign a material, the menu hangs for 30 seconds to appear.
Personally, my material base is on the server, and it doesn't take more than 2 seconds to display the data composed of the SolidWorks base library and the custom library. So placing it on the hard drive shouldn't be worse!
As indicated by @Lucas check the path of the material base in the options.