Hi!
I think the problem is related to your testcase setup; when setting the property mode to step, it will only be increased when the step is executed in any one of the threads in your loadtest, which will most likely result in the behavior you are getting (ie the same value used by different threads), and using mode = READ will of course give you different values each time you use the property, which won't work since you want the same value in all requests.
You will probably need to use a shared DataSource instead, set it to type "Script" and create a script that returns a new number each time..
hope this helps!
regards,
/Ole
eviware.com