I followed all the advice yesterday but was unable to get out of the Finder loop. I rebooted into disk repair (holding down option-r) and my disk was fine.
I finally followed instructions for creating a 'bootable mavericks usb install drive'. You can google this but I used the following: http://arstechnica.com/apple/2013/10/how-to-make-your-own-bootable-os-x-10-9-mav ericks-usb-install-drive/
You must have a USB drive larger than 8 GB! or a double DVD. You also need another computer to download Mavericks again. I borrowed one from a friend.
The install from the USB drive was uneventful and everything works perfectly today. I can only assume the original install was corrupted during downloads.