Processor freeze and RTK exception

My program does (among other things) the controlling of two i2c led drivers.

i update the led-drivers every system-tick (18.5 ms) and run a fading algorithm on every channel (6 rgb leds, so (3x6) channels to recalculate the value of every system-tick)
this works fine for some time, but after a random amount of time (usually between 1 en 5 minutes) the processor freezes. (did it 3 times while writing this post)

it blurts out this information and then resets itself (at wich point M2M studio becomes allergic of my processor and stops playing nice)
Trace RTK 1 Except RTK …144 a 0
Trace RTK 1 ================== RTK STATUS start ==================
Trace RTK 1 ================== RTK STATUS end ==================

i haven’t been able to find any information regarding this error-code.
maybe someone here can shed some light on this problem?