I've had an odd problem recently where MagicSpam silently stops working. I get no notifications, the only way I know about it is when my customers call up.
I'm running a Centos 5, Plesk 9.5.2 Qmail server, and have just updated to release 1.0.4-8 (although this happened on 1.0.4-7 too)
I've tried reinstalling the software too, but it makes no difference.