These link errors suggest that certain classes in your application either haven't been compiled using STLPort or have been omitted from the build. They do not suggest that you aren't linking against STLport.
My guesses would be that:
- The build settings for MyClass somehow overwrite the project-wide setting for the include path and thus MyClass is being built using the default C++ STL implementation and not STLport. This should be easy to check - run dumpbin against the object file and check the functions in there reference the standard library in the stlp_* namespace or not. If not, it's likely that the compiler is not picking up the correct include path. I'd also have a look at the command line that the IDE is calling the compiler with. These can be viewed via the C/C++ Configuration properties as well.
- As other posters also mentioned, there is a chance that MyClass isn't being built, but that should be very easy to check.