Local install of WPMU using MAMP (Mac)

Hi

I've searched in the forums and found related topics but not one that answers this directly.

I know it is outside of wpmudev's remit strictly speaking but am sure some of you must have done it and would appreciate the help.

I have done pretty much a default install of MAMP and successfully downloaded and installed a local version of WP. Woo hoo.

But when I try to Create a network, I get the error:
Error: You cannot install a network of sites with your server address.
You cannot use port numbers such as :8888.

(My DB_HOST is localhost:8888).

I can tell from other posts that people have ermmm, mapped their localhost to something else, and if anyone could tell me how I'd be much obliged. You may have guessed I don't know what I'm talking about...

Thanks