I meant UNC path, it adds the http specific part to the sites root UNC instead of using the UNC specified as a mapping..
Logical Path = /SharedFiles Directory Path =\\webroot\sites\_SharedFiles
URL http://somesite.com/SharedFiles/
CF8 \\webroot\sites\_SharedFiles\ returns \\webroot\sites\_SharedFiles\
CF10\\webroot\sites\_SharedFiles\returns \\webroot\sites\somesite\_SharedFiles\