I think this happened to me before,
Don’t know why this happens only that I send vars through a different way.
Within the <object>…</object> tag you got some params. Add the following param:
<param name=“FlashVars” value="&var1=value1&var2=value2&" />
and in the following <embed> add this attribute:
FlashVars="&var1=value1&var2=value2&"
To make things work in firefox mozilla. So skip the .swf?variable=a and do it my way.
Check to be sure the _root.varname to see if the vars are loaded properly before building ahead.