I've got the problem with virtual path.

If to open the first page after starting application googlesitemap.xml and to use virtual path, the variable SettingsKeyProvider.UsingVirtualPathProvider is set to false when GoogleSiteMap.ascx is loading in CMSAbstractDataProperties::LoadTransformation.

And SettingsKeyProvider.UsingVirtualPathProvide is setted to true only after exception that path is not exist.

Inserting "<add key="CMSUseVirtualPathProvider" value="true" />" into Web.config is useless.

So, to solve this problem I inserted
SettingsKeyProvider.UsingVirtualPathProvider = true;
into Application_Start function.

Best regards, Vladislav.