I think that the implementation of BookmarkValid it's not ok for
IBOQuery (TDataSet).

If we do:

var
Bm : TBookmark;
Ts : Boolean;
begin
Bm := IBOQTest.GetBookmark;
Ts := BookmarkValid( Bm );
...

We got this results:
If CurrentRecord is BOF or anywhere else, Ts=False;
If CurrentRecord is EOF we Ts=True;

However, if we do GotoBookmark( Bm ) it works!

It must return True in all cases, don't it?

Regards,

Artur Anjos