XML does not like ampersands ( & ). In theory you are supposed to URL encode an & as & (I hope that works).

If we are looking at mass URL changes it would make a lot more sense to move to the CJ format of qksrv.net/image-AID-PID than the beFree format that will be increasing awkward for sites trying to meet W3C standards.

The CJ program that delivers images from the affiliate network (the image itself works as the tracking id) is preferable to the BeFree method where you have to use 1x1 image.

In other words...not only would it be a big hassle to have to change links, but CJ has a better format.