Problem adding a record with vb6

I have visual basic 6 with sp6 and I'm trying to add data to PG table, but it gives a error msg like this:

Current recordset doesn't support updating. This may be a limitation of the provider or of the selected locktype.

and I don't know what can it be, this is the code that I use:

strSql = "Provider=PostgreSQL; User ID=postgres; Password=mykey; data source=mypc; location=mybd;"
conex.Open strSql

strSql = "select * from prueba limit 1"
rsTabla.Open strSql, conex, adOpenKeyset

rsTabla.AddNew
rsTabla!ced = 1
rsTabla!nombre = "prueba"
rsTabla.Update

just when arrive to add method explode

some advice???

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