Hi Mike,
I've just had the same problem happen as in this thread here. I'm still looking for which module it is conflicting with, but there needs to be a clean way around the problem because I've seen the same dll in at least a couple of other modules.
Can I perhaps disable the ajax bits for this module if it's only using it for the sort order?
Regards,
Rob
p.s. I've just found the other module.. it's the eTailer ecommerce module - It uses version 1.0.20229.0 of the AjaxControlToolkit.dll