So after a good thread of discussion relating to a post I made yesterday, I've implemented a custom publisher for the ExceptionManagment Application Block. I've simply switched off the Default publisher and routed exceptions to my custom publisher, which logs my exception somewhere other than the Event Log.
Why did I need to do this? Well, there really seem to be some issues with publishing to the Event Log under 2003 with a low trust impersonated account under IIS. Trust me, it's not a simple registry permissions issue with the impersonated account... Anyhow, publishing to the event log isn't so great so the point is really moot. For one thing, event logs can fill up and cause errors, and on top of that permission problems can be tricky at the very least.
With the version of the Exception Management block that I'm using, it doesn't appear to be possible to turn off logging to the Event Log without creating a custom publisher, but it turns out that this is quite easy, so that's what I ended up doing.. See a good article here. Thanks to Sebastien too for all his help with this.
-B