The general pattern for ett words is different if it ends in a vowel.
Ends in a consonant:
a letter: ett brev
several letters: flera brev (the same)
the letter: brevet (-et)
the letters: breven (-en)
Ends in a vowel:
an apple: ett äpple
several apples: flera äpplen (-n)
the apple: äpplet (-t)
the apples: äpplena (-na)
Interesting you should say that; I got an error message here saying that my Flash had a problem or something, and suggesting that I reload the page. Reloading the page took care of it. But maybe, if you're having problems here, too, it's a bug. If you haven't managed to get the audio to work, you can send a bug report.