Today I succeeded in creating working event receivers for my custom list in a MOSS 2007 environment.
I had some difficulties to get those EventReceivers fired. I started with ItemAdding and ItemUpdating events. Those where installed and fired correctly.
But I actually needed the ItemAdded and ItemUpdated events. So I switched to them. And there the problems started.
One big problem is the caching (or something like that) of the elements.xml file of the feature (between brackets: don't forget to change the events in the elements.xml file!). Upgrade of the solution won't work!
You need to uninstall and remove the feature from the solution store. Make sure that all files of the feature are gone from the 12-hive\template\features\-folder.
To make sure that you really get rid of all the old version feature settings, do a IISRESET /NOFORCE. Until I did this, SharePoint remembers some settings of the old version feature. This is quit anoying and frustating and took me a while to get this sort out.