Can't Write To Database After Express SP2

I have a lot of databases under SQL Server Express 2005, reading an writing datas with VB6 (yes Visual Basic 6) and ADO (Provider SQLOLEDB). I do NOT install the SP2, but yesterday I install Silverlight and now I have SP2 on my SQL Server (9.0.3042) !?

Now I have a strange problem: I can read all datas, but I can't write any data to any tables.

Here a simple example:


I have a table "Professions", one column "RecNo" as int identity (1,1) with primary key and a column "Profession" as nvarchar(30).


Reading like this works:

Dim rcs As New Recordset

sTmp = "select * from Professions order by Profession"
rcs.Open sTmp, gcn, adOpenForwardOnly, adLockReadOnly
If rcs.RecordCount > 0 Then
Do
...
rcs.MoveNext
Loop Until rcs.EOF
End If
rcs.Close

Writing like this doesn't work anymore:

Dim lNewRecNo as long
Dim rcs As New Recordset

sTmp = "select * from Professions where RecNo = 42"
rcs.Open sTmp, gcn, adOpenKeyset, adLockOptimistic
If rcs.RecordCount < 1 Then rcs.AddNew
rcs!Profession = "XYZ"
rcs.Update
lNewRecNo = CNull2Val(rcs!RecNo)
rcs.Close


The rcs-object still give me the new record number after rcs.update, but the record is not in the database table. Adding a record in the Management Studio gives an error "row failed on retrieve on last operation". If I then click the button "Execute SQL" the new record is shown.
Another behaviour: Adding a row in the IDE like described above locks the Management Studio. From where I recieve a time out error then click the button "Execute SQL".
Any ideas whats wrong ?