Affiliate Marketing Secrets

I have a 3-month old site (my first) with which I directly sell my own product (as a vendor) through Clickbank. However I have just seen that a search on Google for any of my keywords now only brings up a certain affiliates hoplink in place of my site. The meta description is mine and the SE results/rankings match those in my Google Webmaster Tools so it definitely should be my direct site link coming up and not an affiliate.
My official site is http://www.teachenglishabroadguide.com
The result that comes up is
http://www.teachenglishabroadguide.com/?hop=andrewghay
A search for “teach english abroad guide” will show this on the first page.
On yahoo it looks fine.
Can anybody tell me if this is some dirty black hat trick by the affiliate and what I should do to get my link back (preferably without losing my rankings)?
I’d be very grateful for any help.