Avid Pro Audio Community - Temporary freezes on Win7

I'd love to learn how to use Pro Tools First, but it's freezing and unfreezing to the point where it is unusable. The freezes start as soon as I open the program, so even the startup takes a long time. Eventually, I get an empty window with a menu, but if I do something harmless like mouse across the menu bar just to see if it's alive, it works for about 30 seconds, then freezes for about 20 seconds. It's approximately 30 seconds on and 20 seconds off, repeatedly. Task Manager shows no CPU usage during either part of the cycle. It does this before even trying to open a project, and does the same thing after opening a project. Avid Link is logged in.

This is version 2019.6.0, running on fully updated Win7Pro. I'm using ASIO4ALL v2.14 for sound I/O, my activation is managed by iLok v5.1.0.2866, and I've got plenty of RAM and disk.

I'd assume it was something wrong with my system, but it's happened on two different machines! One even has a freshly installed Win7.

What can I do to diagnose this? Google turned up no evidence of anyone else having this problem.

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Update:

This is behaving like the GUI's main message loop is attempting some operation every 30 seconds that takes 20 seconds to time out. Normally, when writing GUI software, one gives time-consuming jobs to other threads, but I'm thinking perhaps it's trying some network or internet communication that is normally nearly instantaneous, but is failing on my machines for some reason.

Does anyone know if Pro Tools does any communication, perhaps to an Avid server, that could be blocked somehow? I'm grasping at straws here. If I can't figure this out, I pretty much have to give up on Pro Tools entirely, since it doesn't work on either of my machines.

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Paul DeRocco
i7-6700K, 16GB RAM, 1TB SSD, Win7Pro, 2560x1600 30" monitor