When you hover over someone's name the "send PM" pops up below their name. When you move your mouse pointer to it, it goes away. Soooo...how exactly do you send a PM?
I never noticed the rollover effect before. Like StormCinder, the options disappear for me before you can get the mouse to them. I'm using IE7 here (at work)
Yeah, if you can't get the rollover function to work, just go ahead and click on their name like Cal says. It takes you to a page that has a "Send this user a Private Message" link.
Works fine for me in Firefox.. so its possible that your java just needs to be updated. If you're not using Sun Java.. I highly recommend it over Microsoft's alternative as its more widely supported on PhP websites such as 'Zam.