we ran into some sort of inconsistent asp bug.. the weirdness of which is documented here... we've worked around it now. fixing the xml page somehow triggered this bug to happen on other pages which were not touched.... asp.net is very odd sometimes... that is why i stay away from it and stick to the C++
http://professionalaspnet.com/archive/2007/04/09/Unable-to-cast-object-of-type-_2700_ASP.masterpage_5F00_master_2700_-to-type-_2700_ASP.masterpage_5F00_master_27002E00_.aspx