I have had this happen a couple of times. Try using yast software management or zypper and find it's blocked by packagekit even though I have no idea how this has been run. I suspect it's a kde thing.

Any ideas on the quickest way to kill it. Maybe there is a lock file somewhere?

What causes it?

I notice right clicking an rpm doesn't offer open with yast any more and suspect this has something to do with it.

Even better how to stop it ever happening again. I'm not very keen on kde getting in the way of installations.