On paste.kde.org an new version/API was installed, which apparently isn't compatible with the pastebin widget. If one tries to paste something on pko, with the widget one gets the error "Please try again later". Which is very confusing. This was confirmed by several users, from several distros. Please fix this, thanks. PS: Also I wasn't able to install another paste service provider.
I do not confirm on Fedora 20 KDE 4.12.5
Yes, it works here *now*, too! Looks like they fixed it. Marking as RESOLVED FIXED