I have a feeling it's your datatypes crashing your system. I had the same problem with the recent version of YAM as well as some other programs using PNGs for their images.
Use a program like Image Studio to batch convert all the GUI images to IFF/ILBM files, preferably in the same palette or colour depth as your Workbench, saving over the original files without renaming them, then try loading YAM again.
I've also found that if you use the V42 replacement picture.datatype from Aminet, although better and faster than the Commodore one, it can corrupt the toolbar images in YAM. There's supposed to be a fix for it but I haven't looked into fixing it.
