I've seen this problem from time to time on other versions, but on the current 4.5 up to 14843 it seems particularly prevalent.
You start up Cyberduck on Windows (8.1)
you double-click a shortcut
you could try to open another browser.
nothing happens, except you'll see a whirling wait cursor, and you may get an unresponsive alert from Windows.
open Cyberduck again
always, Cyberduck now works as expected.
That's the story. It's possible a connection to phone home about a version might fail by hanging. Connections occasionally do on this cable-based broadband. If that locks up Cyberduck's functioning until the phone-home got through, that could account for these symptoms. Just an idea, and possible frame for a solution if so - a timeout of not too long for phone-home.
2014-06-29 23:33:21,080 [background-1] FATAL ch.cyberduck.ui.AbstractController - Unhandled exception running background task null
at cli.System.Collections.Generic.Dictionary$$00602.Insert(Unknown Source)
at cli.System.Collections.Generic.Dictionary$$00602.set_Item(Unknown Source)
at cli.Ch.Cyberduck.Core.I18n.LocaleImpl.ReadBundleIntoCache(Unknown Source)
at cli.Ch.Cyberduck.Core.I18n.LocaleImpl.localize(Unknown Source)
Yes, this issue appears fixed. I tried it as soon as the update appeared, but wanted to try it again, and did today on receipt of your note. No such problem observed now, so thank you on that; I think you and your team got it.
There is one other problem I saw, just after installation. I ran Cyberduck, no problem, closed it, and tried to run again. No Cyberduck appeared, so thinking I'd missed clicking the icon, I tried again. Still no result, so I looked at the Task Manager and found two Cyberducks running silently in the background.
Mysteriously, I couldn't succeed at End Task on either of these in any usual way - this was a hard block, tempting to thing that Cyberduck was lost somewhere in a driver.
I waited, perhaps a minute, and then both unruly Cyberducks self-closed. After this, I could start and stop them very rapidly, without any ghost processes or duplicate executions.
I'm enclosing the log afresh, in hopes you might find something there. I had a feeling this occurred perhaps due to just running the updater, but it's only a feeling, and with some basis in that the problem went away once we moved away from that time period.