Hi Bojan,
the msp430 is best for such questions. What I do know is that the msp FET has a different power pin for external vs FET powered usage. So perhaps you are seeing some type of conflict there. The only known issue I am aware of - in an older ccs version the dll was no quite handling the external powering correctly. This is fixed in current releases.
I would confirm it is to do with how you are powering things. If this is the root cause, the msp forum is the best place to ask a few further questions.
Best Regards,
Lisa