So strange....and i need ur help
Every time i test my course on Firefox or IE, an error appears and i can not find a solution.......

the error appears like that:

"003_textbox constructor 'g_oSlideFrame' is null or not an object"

Actually, i've reviewed all the actions, objects and codes, but unfortunately can not find a solution.....does any one have an idea about that?

It happened to me when I removed some objects; apparently not all methods were removed.
I would make a copy of your course an delete slides one by one until the message disappears. Then rebuild this slide.
Cheers.[:)]