When I tried to download new settings in my CM15A, I keep getting this error message..."Down load error" there's not enough space in the interface to download your timers & macros???
It sounds like you might have a corrupt AHX file.
Try this:
Unplug the CM15A (USB and power)
Remove the batteries
reboot the PC
Wait at least 5 minutes after having removed the CM15A's batteries, then put them back in.
Plug the CM15A back in (power and USB)
Clear the interface memory
Start a new AHX file, with one or two simple timers and/or macros (for testing - no point spending time re-creating it all yet).
Try downloading to the CM15A.
Let us know if that helps.