As I said, I haven't used such programs, but this much I know:

You can block the connection (not getting on-line at all without a password), you can block spesific programs (Limewire being one), block a group of defined programs (P2P, downloaders, IRC, etc), block spesific web-sites, or block anything that has spesific words in them.

You may be allowed to surf the Web and even visit Limewire-site and download the program in a web-browser, but you are not allowed to use Limewire since this is a whole new dimension to using the Net.

If they don't know what to do, read the manual. Sit down with them on the computer and make the modifications yourself, under their supervision, to allow Limewire to use the connection when you are using the computer.

If you don't get this to work, tell us which program you are using for parental control. If needed, I will download it and see if it can be altered. Be spesific though, a version number of the program is always a good help.