Request a new IP address from your ISP server.

Here's how to do it in windows:
1. Click Start
2. Click run
3. In the run box type cmd.exe and click OK
4. When the command prompt opens type the following. ENTER after each new line.

ipconfig /flushdns
ipconfig /release
ipconfig /renew
exit

5. Erase your cookies in whatever browser you are using.
6. Try the rapidshare download again.

Frequently you will be assigned a new IP address when this happens. Sometime you will, sometimes you will not. If you are on a fixed IP address, this method will not work. To be honest, I do not know how to do this in linux/unix/etc. If this works for you, you may want to save the above commands into a batch file, and just run it when you need it.