Ruud, I just ran the standard Parameter Fit LM.vi (search examples for levenberg) on both LV6.1 and 7 on the same computer (400 MHz AMD, 96 Mb RAM, Win XP Pro) with the default inputs, except I set the total pts to 2000. Both gave equivalent results in 24 s.
Perhaps it's some other conflict on your setup or your modified vi. You may want to run the same experiment to see if it truly is the L-M routine or something else.
