Version:            (using KDE 4.2.0)
Compiler:          gcc version 4.1.2 (Gentoo 4.1.2 p1.1) 
OS:                Linux
Installed from:    Gentoo Packages

Steps to reproduce:
1) Open an instance of Konsole, System Settings or another program with X-DBUS-StartupType=Unique
2) Try opening another instance via krunner or a hotkey.

Result:
The program launches, but a "KDEinit could not launch..." error appears.

This used to work as expected in KDE 4.1.96. No error appeared. 

From what I observed, the following conditions have to be met for the bug to manifest itself:
1) The .desktop has X-DBUS-StartupType=Unique
2) X-DBUS-ServiceName is not defined
3) At least one instance needs to be running already
4) The program needs to be run via krunner or a hotkey.

The debug from matchesPendingRequest:
appId= ":1.60" newAppId= ":1.60" pendingAppId= "*.konsole"
appName= "60"

It seems the numeric appId is at fault. It causes the function to return false.

Reverting commit 911168 works around the bug.