If you are using feedburner and a ical plugin that generates feeds, then please use the http://flagrantdisregard.com/feedburner/, rather than the feedsmith plugin.
The FD plugin allows for the possibility of some other feed (like an ical feed naturally!) and so will not hijack your ics feed like the feedsmith one does.
- a simple hack to the google feedsmith plugin to check the global $feed variable and bail if it = ‘ics’ would also do the trick!
- or if you maintain good coding standards and don’t like editing external plugins (not a good idea generally!), then you could muck around with the wordpress action template_redirect and see if you can remove the feedburner redirect IF it is a ics feed.