This can be caused by illegal instructions (80000000.00000004) such as new
68020/30/40 instructions or inline 68881/882 code.  But this is usually
caused by a word or longword access at an odd address.  This is legal on
the 68020 and above, but will generate an Address Error
(80000000.00000003) on a 68000 or 68010.  This can be caused by using
uninitialized pointers, using freed memory, or using system structures
improperly (for example, referencing into IntuiMessage->IAddress as a
struct Gadget *  on a non-Gadget message).