Access to the temp directory is denied in IIS 7
if you face "Access to the temp directory is denied. Identity 'IIS APPPOOL\ASP.NET V2.0' under which XmlSerializer is running does not have sufficient permission to access the temp directory. CodeDom will use the user account the process is using to do the..." while loading a web page.Please check settings of ApplicationPool identity.
here is a screen shot;
best of luck...