Count Squares with 500Hz

[XS-er]

Hi!
 
I'm generating with the ExpressVI "Simulate Signal" a Square with the maximum frequency of 500Hz (it varies). Now I want to count the falling flanks.
I tried this with the "Trigger Counter.vi"-Example which I slightly changed for my purposes. (see attached file) But it seems as if the Counter is not fast enough for my Signal (- it counts too slow).
 
Anybody an idea how I can solve the problem and count the correct value of squares?
 
Shorty to my system: I tried it with a 2GHz Sempron with LabView8 
                                      and with a 1,3GHz Centrino with LabView7.1
 
Thank you in advance
  Hendrik

[Conseils]

In the simulate signal Express VI the value of one point is set, perhaps you need to set this parameter higher to simulate a real time Frequency.

Try setting it to 100 for example.