I use keys to connect so its not an ssh-askpass issue, though I’ve seen it mentioned elsewhere that some other people have the same issue with connecting using passwords and may have misdiagnosed why the fix works.

virt-manager run as root connects just fine.
virt-manager run as a user hangs trying to connect.  (this is on arch X86-64 client , Centos 6 remote host, but I’m pretty sure the issue is local )
virt-manager run as a user with the command line option –no-fork connects just fine.

I actually only tried –no-fork to gain some extra output on the terminal that might hint at the issue. But it fixes the problem!

I have had a look for similar bug reports on Arch and virt-manager bugtrackers but they’ve been closed as ‘upstream’ and ‘not a bug’ respectively so I’m not banging my head against that bug wall.

So try

virt-manager --no-fork

if you can’t connect to a remote host. You can add the switch to the menu entry on Kde, Gnome etc.