Hi again,
 
Following Phil's suggestion, I removed the .even statement
from asm.h.  The resulting kernel (with DIAGNOSTIC enabled)
panics immediately with "pmap_release count" in pc532/pmap.c.
Compiling without DIAGNOSTIC, a slightly older kernel appears
to run just fine.
 
Herer are the relevant lines from pc532/pmap.c:
 
#ifdef DIAGNOSTIC
        /* sometimes 1, sometimes 0; could rearrange pmap_destroy */
        if (pmap->pm_count != 1)
                panic("pmap_release count");
#endif
 
Sverre