I see. Any idea where to go from here? Setting things seems to be OK but nothing from Miscellaneous Stuff or Scripting loads.
"bad magicnum" would normally mean something is corrupted, either the module files or camera memory. Try a different card or re-formatting and reinstalling. If the file were the wrong version or mission, the error would be different.
It's possible that some other bug could cause this, but if it were a generic bug in chdk code one would expect all cameras to be affected.
As always, input from other users with this camera would be helpful.