Same process in Cubase, my load screen occasional hangs when it scans the plug in folders, and I've never tracked down which is the culprit. I suspect it's when it decides a plugin is to go to blacklist status. Can you take the plugins and take clumps of them into a new folder outside the vst search and narrow it down. Again, no proof, but I wonder if it's not always the new vst, but a combination of the new and the old? Perfectly fine before instant ion and later, after too, but a pain on first install.
I assume you've already tried just removing it? Have you tried putting it in a different vst folder?