Ado Append / Post does not work

hi,
if i do the following:
AdoDataset.Append;
AdoDataset.Post;
so to insert a totally blank record,
ado complains that either bof or eof is true (target is Sql Server 2000)
if i set a field value to something then the error goes away
is this a behaviour by design? thus can't i create an empty record this way?
(i want to do this to have the primary key set)
all the fields in the sql server table have the AllowNulls set to true so
creating an empty record should be possible
...
tia,
marc