menotu
Interesting, yesterday I did not seem to have any problem opening KGet but today I get the symptombs, I see the flutter in the panel and then all goes quiet. trying to start again from konsole I am told it is already running, well a bit more:
[gert@localhost ~]$ kget
QDBusConnection: session D-Bus connection created before QCoreApplication. Application may misbehave.
kget is already running!
QDBusConnection: session D-Bus connection created before QCoreApplication. Application may misbehave.
[gert@localhost ~]$
SEARCH on Forum landed me here and following your lead I looked in tray Entries, and changed the entry to Always Visible
I can live with that I think, at least while experimenting as I have just installed KGet to see what I can make it do. 
Hey
wedgetail If you happen to get the
already running message you could have a quick look in
System Activity using the
Ctrl+Esc key combination and have a browse to see if there are actually more than one process running.
The screenshot below shows my
kget system activity and correctly shows only one process running
If there is more than one process you can stop it or
kill it by right clicking on the process and choose
Send Signal > Kill
When kget is in the process of downloading a file it will naturally show more than one process - see below
