I guess you're referring to the TradeTracker UK feed? I downloaded the latest Interhome datafeed and affiliate links redirect to an error page.
This is a link straight from the datafeed
Replace 35684 with your affiliate ID and you'll see the link does not redirect properly.
So there is a problem on merchant's (or TradeTracker's) end.
Best is to contact the merchant or to log a support ticket in TradeTracker and report the issue.