[eluser]Randy Casburn[/eluser]
You've not provided enough information here. Can assume you're calling a Model called Customer from some Controller. This could be several things like a case problem with file names vs. class names. That often causes problems. Go back and review the documentation to ensure you very clearly understand where the capitalization must be in the Class names and the file names.
Can you put relevant code that calls your Model here and let's take a look.
Randy