The error message is "Memory Card Error" and in Options, 'Format' is greyed-out. I don't know how to get more error information.
I used Disk Manager in Windows to delete the volume, and created a new FAT32 partition. Problem persists.
Weird, I'm not aware of anyone reporting issues like this. If it is really a formatting / partitioning issue, it's possible that some other tool would fix it, but given that 32GB cards are under $5, just getting a fresh one might be the best approach.
If you do want to keep messing with it, a few ideas
1) With disk manager, delete everything all volumes/partitions from the card, eject the card, and then format it in explorer (you want to format the entire card, which will be the default in explorer, where in disk manager you might inadvertently end up with a more complicated partition table setup)
2) Use an SD specific format tool like the one from the SD card association
https://www.sdcard.org/downloads/formatter/ (some SD card vendors may offer their own tools)
3) Use linux and something like gparted to examine the current configuration and/or delete whatever is there. There are various live (usb/cd bootable) distros available if you don't have a linux system.
edit:
One other thing, since the card was presumably locked when you used it with CHDK, make sure the card lock is completely in the unlock position. The camera should just say "card locked" if it's locked, but maybe it could cause problems in combination with other issues.