I changed the setting in KDE control center to read "firefox%u" and will see if that makes a difference. I may have to restart KDE so let me see what I can do...
I don't think changing anything in Open Office is the solution as many apps use Konq rather than Firefox so I would assume it's KDE not the application that is the problem.
In case of Thunderbird it is very likely the application's fault.
Mozilla's applications have very bad desktop integration, so they usually launch "something"
I am not sure how the OpenOffice KDE Integration handles launching, but it might be at fault as well.
One good way to configure launching in external (non-KDE) applications is to use
kfmclient exec %u
as the command, because kfmclient exec will then use whatever you set in Control Centre