For some reason I'm not getting any notifications when someone replies to a thread I started or I posted in and am following. Here is a screen shot of my alerts page
Look under the generic "preferences" page, and make sure the first two option are checked regarding automatically watching a thread and receiving e-mail alerts.
Mike, pick a thread you are not already "watching" and manually watch it, turn on email notification in the dialog box that pops up. Let me know if you get email from that one.
I have the opposite problem. There are threads that I participated in during the early days of the site starting up, and they keep sending me emails despite changing my setttings. I got them to stop by manually responding to each one I get, disabling the email notification. Now if only the junk mail senders would listen.....