Flash acting strangely in Firefox

[plantpot48]

Hi I'm new to Flash, so an explanation of the problem below would be very useful!

I have a small login section written in Flash that works like this:

A parameter (sUserName) is passed in Param/Embed to say whether the user is logged in or not.

If sUserName is undefined, username and password boxes are displayed with code to pass the details to PHP for login.

If sUserName is passed, then flash executes a gotoAndStop(2) - Frame 2 being where the username is displayed indicating the user is logged in.

This worked absolutely fine in IE and Opera but not in Firefox where the content in the 2nd frame would not be displayed.
To fix it I had to change "gotoAndStop(2)" to just "play()" with a "stop()" in frame 2.

Why would these statements cause different results since, in effect, they mean the same.

Ta