It Might be that the screenmode prefs file has somehow got screwed, so this will need remaking.
The system will hang if any requestor is opened durring the bootsequence, cxg simply doesnt like it and is usualy visable by black boxes opening ontop of the boot pic.
Solution ....hmm, if you made an emergancy boot floppy with all the screenmodes setup, it might be possable to boot that and simply copy the screenmodes prefs file over to the hd.