Error Message: libraryElements is null

In the past several months I’ve installed 5.0beta x86 on a PC from an upgrade path from 3.27. I’ve never had a problem starting up the User Manager from router_ip/userman.

But this time (and several times over the past few days), I installed 5.0rc without going through an upgrade path.

After I start up User Manage and put in user/pass, I get the pop up window that says:

The following client application has occurred:

Cannot process ServerMessage (Phase 1)

Error Name: TypeError
Error Message: libraryElements is null

If I go back and install 3.27, then upgrade to 5.0rc1 x86, User Manage has no problems.

Any suggestions what I might be doing wrong?


Update: I tried the following to narrow the scope of the issue.
Direct install with 5.0beta and UM fails
Direct install with 5.0rc and UM fails
Upgrade from 3.27 to 5.0beta and UM works
Upgrade from 3.27 to 5.0rc and UM works