See my post from a few days ago. I thought I had done damage to my camera after stupidly trying to clean the mirrors and sensor with a cloth.
I cannot recommend enough the Arctic butterfly, which although very expensive for what it is, is a very good piece of kit.
With a model as refined as the 40D, surely having the best equipment to maintain it is a must too?
Glad your camera is ok though. That feeling that you might have damaged it through doing something stupid is something I never want to experience again!
Out of interest, I contacted a camera repair shop for a quote to replace my sensor on a 30D. (They wanted over £300 + VAT!!)
So my advice, buy the proper tools for the job!