this happens everytime i run asp.net configuration 

Server Error in '/asp.netwebadminfiles' Application.

Compilation Error

Description:An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately.

Compiler Error Message: CS0122: 'System.Configuration.StringUtil' is inaccessible due to its protection level

Source Error:

Line 988:             // Put together some unique app idLine 989:             string appId = StringUtil.GetNonRandomizedHashCode(String.Concat(appPath, appPhysPath)).ToString("x", CultureInfo.InvariantCulture);Line 990: