Yeah sorry, i made a mistake while typing the truncate.

I think i found an explanation to this behavior :

http://sqlblogcasts.com/blogs/tonyrogerson/archive/2006/11/16/1345.aspx

http://www2.sqlblog.com/blogs/alexander_kuznetsov/archive/2009/04/10/selects-under-read-committed-and-repeatable-read-may-return-incorrect-results.aspx

The update of the bit field made the select return the row twice. Before today, i was 100% sure that this was impossible!