You can check here:http://chdk.wikia.com/wiki/FAQ#Q._How_can_I_get_the_original_firmware_version_number_of_my_camera.3F
and confirm that you have the correct version of firmware on your camera (each load of CHDK is custom to each camera version of firmware).
I don't know what else is wrong unless you accidentally picked up the wrong CHDK programs (like A650 instead of A560). It is also possible that a particular build has a bug... Check the site for a new build (new date) or one of the various other CHDK "family" programs produced by other's (like Microfunguy or Fingalo).
Lastly, have you tried the DISKBOOT.BIN version of the program (format card to FAT16, copy *.BIN to card root, make card bootable, write protect, then turn on camera in any mode)?
PS: CHDK is not a "Firmware Upgrade"--it does not rewrite any of the software/firmware inside of the camera no matter how you load it.
Instead, CHDK is more like a software application on your computer. You load the software each time you want (either through the "Firmware Upgrade" option (which tell's the camera's internal firmware to load whatever is on the memory card in the *.FIR file) or during the camera boot processes (where the camera checks if the card is FAT16, the card has been marked "bootable", the card is write-protected, and there is a file named DISKBOOT.BIN on the card)...
In either method, the CHDK program is loaded into "main memory" and control turned over to the loaded CHDK program... At that point (from what little I know) the CHDK program calls the normal Cannon boot code and the camera finishes booting then returns to overall control to the CHDK program/application still running in main memory.
CHDK then intercepts key presses and other camera functions and then either does some work on its own, or simply calls one of the camera's own function to perform the desired actions.
Once you turn your camera off--the CHDK program in memory "goes away"--and you start the whole process over again the next time the camera is turned on... -BB