MUIE_OK	-	no error, everything allright.
MUIE_OutOfMemory	-	went out of memory.
MUIE_OutOfGfxMemory	-	went out of graphics memory.
MUIE_InvalidWindowObject	-	NULL window specified.
MUIE_MissingLibrary	-	can't open a needed library.
MUIE_NoARexx	-	unable to create arexx port.
MUIE_SingleTask	-	application is already running.