I have tried so many thing but i can't resolve that Error. I can connect with my username and password to: Database in SQLDeveloper, in SQL-Plus, in Server-Explorer (Visual Studio 2008) and all works fine. But if i Compile my Project i get that Error. Why is that? I tried to set case_sensitive to false, but the same error appears. I dont know what else to do. My Oracle version: Oracle Database 11g Express Edtiton Release 11.2.0.2.0 - Production PL/SQL Release 11.2.0.2.0 - Production CORE 11.2.0.2.0 Production TNS for 32-bit Windows: Version 11.2.0.2.0 - Production NLSRTL Version 11.2.0.2.0 - Production