I have to agree with Van on this one, Microsoft does not like the open source platforms all that well. They don't like giving fixes for anything that they do not have their hands into.
I can say this though- if your server is set up to support ASp and it does not cost extra to you, you can embed ASP code using PHP or you can just use ASp for that particular function. But I assume that you do not have this capability or you would not have posted on here.
I just did a search and I can't find a real fix either. You might want to try a simple redirect without the 301 heading, this will be picked up by Google anyway, and you are more likely to be picked up by spiders as well.
If you are concerned about your rating on a Google or another search engine or directory, I suggesting taking a look at this site (They have lots of good info for you):
http://searchenginewatch.com/webmasters/