Problem with serial counters

When I install my application, I use a SQL script to create the different tables.
Most of my tables start with a Serial column called RowId.
In my setup script I insert a few records into some tables, providing all fields, including the RowId (1, 2, 3, etc).

The problem I have is that when my user tries to insert a new record without the RowId field,
Postgres complains that it finds a duplicate key.
I guess when I do an insert with all the fields (including the RowId), Postgres does not increment the serial counter.

I cannot remove the RowId field from the Insert of my setup script because this setup script is also used by customers using MySQL.

What can I do to force PostGres to update the internat serial counter when I do an insert with a specified value for the serial?

Jacques Lebrun
Web Mobile Inc
819-563-0133
JLebrun(at)cplus(dot)org