I ran into a similar situation when I wanted to add Recently Viewed to the search results page. After dumping things for a while I found that I had to change the following line in recentlyviewed.xml.config:
Code:
<queryparam paramname="@customerGUID" paramtype="runtime" requestparamname="custGuid" sqlDataType="nvarchar" defvalue="" validationpattern="" />
to
Code:
<queryparam paramname="@customerGUID" paramtype="system" requestparamname="CustomerID" sqlDataType="nvarchar" defvalue="" validationpattern="" />
Since the change was only needed in certain circumstances I created a copy of the original and renamed it to MOD_recentlyviewed.xml.config so I could keep the original functionality as well.
This may not be the case for you, but hope it helps.
Rob