Seems other are at least able to login with 2.5 ... not me!
In fact, I wasn't even given the option to upgrade -- a freakin' DOS window opens, the upgrade starts, I'm asked whether to allow to connect, I say no repeatedly, the upgrade proceeds anyway.
Now I'm left with a viewer that says it can't resolve the host name, and no access.
So, I uninstall the viewer, re-install 2.4, and guess what? Forced to upgrade again. Same result.
Lovely. Thank you very much.