Sorry, but I want to be sure you get this. If I'm setting up the Munchkin party e-vites, I need details, but first try this

in myspace, click mail, then event invites (left side), then click any event e-vite ever. click "view event". when the next page loads, look at the top right side of the page for a link for new event.

it looks like it's a myspace flaw, but if you really can't do it, I'll take care of it for you.