Falling snow for Flash CS4 / AS3

Hi Dear,

I refer to the following URL :
http://www.kirupa.com/developer/flashcs4/falling_snow_as3_cs4_pg5.htm

The actionscript is applied on my FLA successfully. Here is a brief description :
(a) frame 01 to 30 : without snow effect
(b) frame 31 to 99 : snow effect applied

There is no problem at all when the SWF is run for the first time. Thereafter, the snow effect keep appearing thoughout the whole SWF. I don’t know why it is so. Please kindly enough to help solving the problem.

Thank you very much.

G. R. ZHANG (MR)