Each time I try to change the setting of any of the parameters inside pyro fx Houdini crashes saying it's a fatal error.

I am using a Macbook Pro 17", 2.8GHz, Intel Core 2 Duo, 4GB 1067 Mhz DDR3
Graphics Cards:
NVIDIA GeForce 9600M GT 512 MB and
NVIDIA GeForce 9400 M 256 MB

4GB DDR3 RAM 1067 MHz

OSX Version - 10.6.4

What could be the possible fix, I am new to Houdini !

It could be a bug, or could be something with your graphics card… Try changing the viewport update to manual instead of automatic and see if you can still change the parameters.
I couldn't reproduce your error so can't say much…
Maybe share the file or part of it.

cheers