Real Time Clock DS1307

Hi there!.

I am using a RTC DS1307 with a PIC18F252 and already write and read the
RTC´s registers by I2C protocol; nevertheless when I consult the
seconds register, I notice that the RTC works 9 times slower of the
normal thing; my theory is that it is due to the crystal that I am
using...., which seems to me strange is the slow thing...

Well, here come my questions...

* Some one know if in fact this device (DS1307) is so sensible when
using an unsuitable crystal?

* Which other factor could influence in this behavior?

* Could be a firmware problem? (I don´t think so)

Many Thanks

Andros!