Also check for any old aga / gfx patches that mighthave got left in the system before installing the bvision.
also delete screenmode.prefs from env:sys/ it might be trying to open an illigal mode. youc can set the screenmode up properly again once wb has loaded. The bvision also does only promote the 4 color aga mode properly, its there just to see you through os instalation upto getting the gfxcard drivers up and running. its not ment for everyday use. so me sure to select a cgx mode as apposed to a pal mode.
Also latest cgx 4.2 is needed to work properly with the os39 bb2 update.
