Posting this just in case someone else runs into the same problems.

The menu bar in the admin area wraps, splitting 'Admin Access Management' to the far right end and also at the far left, followed by 'Extras'. This makes it nearly impossible to access the drop down list. I solved this issue by editing /admin/includes/languages/english.php and shortening the label to 'Admin'. Maybe I'm the last developer still using a 17" CRT?! :)

I've been using wamp for years and it never had an issue with zencart. However, I recently upgraded to the latest wamp and then tried upgrading 139H to 150. Everything in the admin that would result in database changes caused endless hangs. For example, trying to install or uninstall a payment module. Even a clean install of zc gave the exact same result. Figuring it must be something to do with wamp, I installed xampp and another fresh install of zc. Problem 'solved'. Maybe it was just a corrupted download. At some point I'll download a fresh copy of wamp and give it another try.