audio malfunction under Mozilla Firefox

I've found this problem using Mozilla Firefox in all these section:

dialogue, vocabulary, expansion and all pronunciation tables,

only the first link in each page it's still active, while all the following links seems to be OK, but it doesn't work at all, no sound can be produced.

I've tried on many different lessons, and everywhere, sadly, the same...

 Using Internet Explorer everything it's OK, but I'd prefer to use Mozilla, is there anybody else in the same condition?

The link to text version in the pdf. for the last lessons it is still not functional, it returns error 404...  I hope this will be fixed, becouse I found extremely useful the text version, being impossible to copy anything directly from the pdf.....

    谢谢,

        再见, michele