I haven't tested it in IE6, I don't have that either. But Generally the first thing I do when trying to see why something isn't working is run it through a validator. Sadly, your page really doesn't work well on a validator, and it runs lots of complaints.
Stating "XHTML Strict" and then using non-strict html really isn't a very sensible idea.
http://validator.w3.org/check?verbose=1&uri=http%3A%2F%2Froofcommunityservices.org%2Fdonations.html
If you are lucky, fixing your 226 validation errors might help IE6.
People who disagree with me, try changing the closing tag of "title" to "titel" , and see the miracle occur where IE renders a completely white page but firefox doesn't mind.
As for getting Flash elements to validate, see here:
http://latrine.dgx.cz/how-to-correctly-insert-a-flash-into-xhtml
http://www.alistapart.com/articles/flashsatay
This has also been useful in the past, but its a bit dated now:
http://jquery.lukelutman.com/plugins/flash/