<...>

> When I checked the IBO code there was indeed SysPost
> function in Insert.

<...>

> Is this normal, or am I missing some parameters somewhere? In
> BeforePost I do some data checking and now the user gets
> errormessage even before he has chance to do anything.

SysPost operates as...

if State = dssSearch then
SysPostSearch( true )
else
if NeedToPost and
( not IsPosting or
( IsRetaining and not IsPostRetaining )) then
begin
<...>
SysBeforePost


So it should only call SysBeforePost when there is a "NeedToPost".
That is, SysPost is called to ensure that any existing changes are
posted prior to starting a new Insert or Edit etc. So it would seem
that for some reason IBO thinks your dataset needs to post. Is there
any chance you are calling Insert recursively somewhere in your
application (check your call stack).

Does this help explain what is happening?

Geoff Worboys
Telesis Computing