Are you using Eclipse Java EE 4.2.2? That's the only supported version for Worklight Studio (i.e. make sure you are not using 4.2.1 or 4.2 alone).
Other things I would try: 1) Use RTC 4.0.3 plug-in instead 4.0.2, that could make some difference and usually these clients have backwards compatibility with the server.
2) Install RTC before Worklight Studio, and see if it makes any difference.