This can be fixed by deleting your F3 folder and re-installing it.
I typically just put the F3 folder on a FAT32 flash drive, boot to the stock dash by holding RB during boot, then use XexMenu to delete the old one, and recopy the new one to the same place.
If you name the folder the same as it was, your console will still boot to F3 automatically without having to change the dashlaunch settings.