Xbee and DS3231 libraries conflicts

Hi. I'm use a Seeeduino Stalker v2.1 with Xbee Module, for this use the Xbee.h library, and i want show date and time, with DS3231 library, but when I begin "RTC.begin()" in the setup the this stop my program. I proved and I have select for use xbee or rtc. Somebody have the same problem? The problem it detect when the program run over SeeedStalker.

Thank you and regards.

No links, no code == no help.