> I changed the field to NOEDIT. The problem is gone.
> All works fine. If I set the field back to READONLY, the problem
> reappears. I suspect there is some strange bug with cachedupdates
> and readonly fields.

Sounds like there is some sort of inconsistency to me. Since I dont
use cached updates myself I am not entirely certain of the expected
situation with readonly fields. However I would like to point out...

IBO sees ReadOnly as meaning that the column should not be included in
insert or edit processing. Although I think that in some instances
this can be overridden by providing custom EditSQL, InsertSQL.

So the correct way to manage your requirement is probably to use
NOEDIT on the column (and even NOINSERT if desired).

hth

--
Geoff Worboys - TeamIBO
Telesis Computing