Getting Error After change Admin URL.

Hello There.! I want to change back-office url and after using google i find out to make some change in Config file i am able to change backoffice url..

where i change

 <add key="umbracoReservedPaths" value="~/MBGCCMS,~/install/" />
 <add key="umbracoPath" value="~/MBGCCMS" />

now i add new package and after successfully adding the package i am getting below error.. change you tell me what i am doing wrong ??

thank you..