On our small business network our old 10/100 consumer grade switch gave up the ghost, and we replaced it with a proper business-grade gigabyte switch. After wiring it in our Linux and Mac users immediately got back to working off of network drives;

But 2 of our 3 Windows 7 PCs have suddenly experienced a tremendous slowdown with mapped network drives; Windows will become stuck "discovering" a folder causing applications to freeze when trying to open files. It will instantly display and browse files, but the moment you try to open one the bug hits. To remedy this we have our users copying files to the desktop, but it can take a few minutes while windows is stuck "calculating" the time it will take to copy. These aren't big files, mostly excel sheets less than 500KB - these operations are instant on Linux and Mac.

(The third Windows machine is having no issues)

I've tried remapping the drives, mapping to different drive letters, rebooting, etc. I'm at a loss, because switches are mostly transparent, and it's only after the switch was replaced that the Windows PCs started acting up. What black-magic voodoo am I missing to make Windows work?

Thank you.