We had a couple of clients who would just never do an initial connection to CrashPlan after the upgrade from CrashPlan 4 to CrashPlan 6.5. But they would never time out or give an error message either.
Restarting the CrashPlan service didn't help. Restarting the computer didn't help. Uninstalling and reinstalling the client didn't help.
Turns out it if the detect-a-user script can't find a CP_USER_HOME, it will just keep trying to connect instead of erroring out. We modified our script, and now those clients are good (we did have to uninstall and reinstall the client after modifying the script, though).
P.S. Someone pointed out that I don't actually share the original or modified script. The point of this blog post isn't to say "Here's a script that works." There are lots of scripts that work. The point is more that if you're experiencing this issue ("connecting" and never timing out or providing an error message), you likely need to fix your script to output a CP_USER_HOME).