Have you read this T3 Spammers; mp3 Bit-Rates Versus File Sizes
Is it that your files say they are corrupt or that when you play them back they have silence? Did you get a message coming up with a message saying corruption detected? Did you tick continue or not to continue & did you tick the always use this answer? If you ticked no then the file will probably have corrupt in its name.

Do this test: Bug Report instructions & sample image Is the result True/False? If False then there's still a firewall issue.

Did you use this Configuring Norton Internet Security for directions for configuring your NIS? Just double-check it.

What modem / router brands & models do you have?