In my experience, the vast majority of these type of situations, it is usually the client end that causes the disconnect or some problem with the ISP rather than the server end.
I agree, but all of his computers at home are MacOS-X and I am quite unfamiliar with MacOS-X myself. That, and this is a guy who thinks he knows everything, so if I tell him something without proof, it's my word against his, and he wins (you know the type). I've already told him to check his side for problems, and of course he insists that there's nothing wrong. This is why I am hoping to be able to find a detailed log of the cause of the disconnections (most likely will simply say something along the lines of "closed by client" or "client connection lost" indicating a problem on his side) so that I can show him that it _really is_ a problem on his side.
Unfortunately, this type of problem is inevitable with this type of person... but when he's the owner of my client, I can't do anything about it other than prove him wrong...
Thanks for your thoughts though! I had thought about doing the site-2-site thing too, but he's on a DHCP cable modem, and I didn't want to have to do an open-ended site-2-site... I might have to though...