Comment # 1 on bug 939454 from Wolfgang Bauer

(In reply to Olaf Martens from comment #0)
> When attempting to do an update packages with Apper it may occasionally
> hang. Especially flash-player is notorious for this when a browser is using
> the plugin, which is especially true under KDE, because it loads Konqueror
> upon startup - and that one locks flash-player, thereby causing Apper (to be
> more precise: packagekitd) to hang.

No, you're misinterpreting the problem.
It doesn't matter whether a component is in use by another process.
Otherwise this would also happen for every KDE update when running KDE, which
it doesn't...

Rather, packagekitd hangs whenever there is a license agreement necessary,
which is the case with flash-player in particular.

> Apper displays "Waiting on other processes", but nothing happens, no matter
> how long you wait.

That's not completely true either.
Any interaction with packagekitd will "wake it up", and it will continue to
install the selected updates.

So other workarounds include:
- right-click on KDE's update icon and choose "Check for new updates" (there
won't be any progress report in the applet in this case, but the updates will
be installed)
- start Apper and check for updates
- run "pkcon get-updates" in a terminal

And it will also continue when Apper automatically checks for updates the next
time. So set the check interval to "hourly" and you'll wait one hour at most...
;)

Anyway, this problem has been reported already, marking as duplicate.

*** This bug has been marked as a duplicate of bug 908730 ***