Comments email

Hi, I’m using WP v 1.2. I’m having a problem with comments email. Up until today it’s always worked flawlessly (meaning I always have gotten the email notification of a comment).
A few days ago I installed the “Subscribe to this comment by email” hack, from Scriptygoddess. It also has worked just fine so far.
However, today I stopped receiving email notification of any kind. I haven’t changed anything on my end; I don’t know what the problem is. No one else is getting them when they click the “subscribe” option, either. Any ideas? Thanks.