Strange loading behaviour

For a few days, when one of my sites loads it is showing a "waiting for" message refering to a site that is nothing to do with mine. A couple of people have also told me that they were mysteriously diverted to other sites - one porn and one embroidery (!). I checked with my ISP and they checked but could see anything at the time. It's still doing so tonight on www.the-confidant.info. What do you reckon is the best way for me to track this down myself?

Thanks, Graham