Jan 15, 2009 07:27 PM|RickNZ|LINK
I'm not sure if this applies in your situation, but a vanilla ampersand is actually illegal in XML, upon which ASP.NET is based. For URLs in .aspx files, be sure to encode them with "&"
OTOH, if you're seeing errors with incoming URLs with ampersands, does the request make it into the .NET page processing pipeline before being rejected? If so, perhaps you could use URL rewriting as a work-around?