v5.1.0.0 has 'Default2006' theme set in ConfigFile.xml and ListConfigFile.xml.
v5.2.0.0 has 'Telerik' theme set in ConfigFile.xml and ListConfigFile.xml.
Setting theme to 'Default2006' causes an error in v5.2.0.0,
'Telerik.Web.UI.RadWindow with ID='ctl00_m_g_81048955_8891_41bb_a762_69647a5955a0_ctl00_ctl05_ctl00_ctl00_ctl00_ctl04_ctl00_ctl00_RadTextField1dialogOpener_Window' was unable to find embedded skin with name 'Default2006'. Please, make sure that you spelled the skin name correctly, or if you want to use a custom skin, set EnableEmbeddedSkins=false.'
v5.2.0.0 has 'Telerik' theme set in ConfigFile.xml and ListConfigFile.xml.
Setting theme to 'Default2006' causes an error in v5.2.0.0,
'Telerik.Web.UI.RadWindow with ID='ctl00_m_g_81048955_8891_41bb_a762_69647a5955a0_ctl00_ctl05_ctl00_ctl00_ctl00_ctl04_ctl00_ctl00_RadTextField1dialogOpener_Window' was unable to find embedded skin with name 'Default2006'. Please, make sure that you spelled the skin name correctly, or if you want to use a custom skin, set EnableEmbeddedSkins=false.'