the menu bar seems to appear if another application is launched - or brings a window to the front - while catalyst is loading.
multiple applications can be launched from the startup items folder at pretty much the exact same time.
it is not the usual behaviour for a launching application to keep itself hidden.
when the other application launches it opens a window which can come in front of catalyst.
the OS keeps track of application which are and are not using full screen mode.
This is not a software bug -- in catalyst. the workaround involves a trick - it is not a bug.