Do you have adequate decoupling for those LED displays - they need a lot, you may be getting interference
from the display if decoupling is poor and/or the wiring layout isn't nice and tight (run all the wires to the display close together to prevent open loops).
[ oh, and most importantly don't share ground wires between chronodot and the LEDs, thats bound to be bad news. Run ground and power separately to each and keep them apart. ]