I have just run into a weird problem, affecting both 2017 R3 and 2019 R2 on the same machine, simultanously. No particular recent change except  Windows 10 updates as usual.

It affects all datawindows. Trying to open any one with the painter, in any target/workspace, there is a delay of up to 6-7 minutes, then the painter opens and everything within it works normally.  Every other painter works normally. Every DW can be accessed with Edit Source as before. Everything compiles fine as before , it's just the slow opening that is affecting both versions of PB. Applications can be compiled and deployed and performs as before. There is also a similar delay when accessing the "Printer Font" tab in System Options. After some minutes it opens, and any options may be edited and saved. 

During the delay, Task Manager reports no activity on PB, 0 Disk and 0 CPU

I have tried: deleting Default DW entry  in registry. Deleting DB interface and inserting it again. Swearing. Rebuilding everything. Rebooting everything.