We get this error in a project in a web application solution which has VSS as source control. The project has a script in the pre-build event command line in the VS 2005 Project property page - Build event is as below :

Code:
copy /d "$(SolutionDir)UX\UserControls\*.ascx" "$(SolutionDir)UX\GetQuotations\ThirdPartyOperator\UserControls"
copy /d "$(SolutionDir)UX\UserControls\*.master" "$(SolutionDir)UX\GetQuotations\ThirdPartyOperator\UserControls"
...