Your sprite name for the cactus (CACTBL) is too long. Sprite names must be four letters followed by the frame letter and angle number, but you have six letters. Instead of CACTBLA0, try CABLA0. Make sure to update the freeslot declaration accordingly, along with the rest of your SOC.
Also, your SOC is incorrect. Use SpriteName = CABL
instead of what you currently have (essentially, remove the SPR_ prefix on that line only, you don't use it in state definitions). You also need to include an = sign after the word "action."
Finally, did you edit the sprite offsets in SLADE at all?