There is a bug reported when printing numbers with the overloaded Serial.Print (http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1256745982/160#160) and I'm not sure it's caused by a stack problem. Sadly we could not work on it yet.
May I suggest that you try with the v0.1 and the 0018 core? These bugs were not reported for that version, and there was a FreeRTOS kernel change between v0.1 and v0.2. If it works, we may roll-back something for the v0.3.
Thanks!
Regards,
Julián