In the interest of fairness, Internet connectivity isn't as reliable in some parts of the world, so it *could* be that his net connection is down, but it would seem that if he knows a bunch of people want him, he'd call somebody and have them post on his behalf.

I'd say file the dispute. If he responds, you can always cancel the dispute. But I agree with Patti that paying in advance is generally an unwise idea unless you really, really know and trust the person.