VERSION:
1.80pr0 (Via FTB Unstable 1.10)
DESCRIPTION:
It crashes.
EXPECTED RESULT:
...Not crashing? (what am I even supposed to put here?)
REPRODUCTION STEPS:

1. Launch Minecraft with CC 1.80pr0 installed.
2. Create a world.
3. Place a turtle (in my case, a mining turtle) in the world.
4. Press F3.
5. Look at the turtle.
   This should result in a crash.

Update: This also occurs (with a similar exception) with a YETA wrench.
Exception is: java.lang.IllegalArgumentException: Cannot set property PropertyDirection{name=facing, clazz=class net.minecraft.util.EnumFacing, values=[north, south, west, east]} to down on block computercraft:CC-TurtleAdvanced, it is not an allowed value

this bug doesn't happen in my case. have you tried replicating the bug again? if so what mods other than computercraft did you have?

This has been solved in pr1 (not yet released)