I've been trying to use a 32.768kHz crystal as the main clock of the PIC mcu and have been running into problems. The chip would get stuck and stop processing.
I've been using it on a bread board and with no 10-15pf grounding caps... Ususally when I use a 4MHz crystal with out caps and on the breadboard I don't get any problems.
Is there a special way of connecting the RTC crystal that is different from a regualar crytal connection?
You should always use capacitors, you may have been lucky with 4MHz crystals - particularly on a breadboard where there is lots of stray capacitance. Why not follow MicroChips recomendations?.
The usual reason is power consumption, a PIC running off a 32KHz crystal has much lower power consumption - you must also remember to set the config fuses to LP of course.