What follows in the post contents is the original description which applied to Iron Portable; it seems now that it's more widespread PortableApps.com Launcher problem. Further information in JonBoy's comment.
The error window itself I get is titled "Iron Portable (PortableApps.com Launcher)"
I installed Iron Portable three times new the last weeks as I always got a "Another instance of IronPortable is starting. Please wait for it to start before launching it again." after a fresh start of windows.
Eventually I also got a "Another instance of IronPortable is already running. Please close other instances of IronPortable before launching IronPortable."
I checked the processes running in the background but no Iron instance found. Closed PortableApps at all, tried to start Iron - fail.
Starting iron.exe from \IronPortable\App\Iron\ does work with none of my profile items loading of course. No plugins, history, etc.
Until now I could only solve it by uninstalling and reinstalling everything from scratch, doing all installs, form data, cookies, etc all over.
Any suggestion what might be wrong?
Thanks a lot for any helpful suggestions to get rid of this problem. Firefox became too much of a ressource hog my laptop couldn't handle anymore (1gb+ ram while running).
[Title updated from "Iron Portable (or maybe PortableApps.com Launcher) error" - mod Chris]