Just thought I'd post an update. After downloading the latest CM nightly via CyanDelta, I clicked the 'Install Zip' button and my phone rebooted into COT and automatically flashed the new ROM. The first text displayed on the COT screen was 'Waiting for SD card to mount (20s)' and on the next line, 'SD Card mounted'. Everything went as expected, but I wasn't able to grab a copy of the recovery.log file as the phone automatically booted into Android after flashing. I then rebooted into COT from Android and the 'Unable to mount SD Card' message was again displayed on the main screen, but COT allowed me to create a Nandroid backup without error.
Hope that helps,
Phone: Sprint Nexus S 4G
ROM: CM10.1 Nightlies
Recovery: ClockWorkMOD 18.104.22.168 Touch Cannibal Open Touch v2.1
CPU Settings: ONDEMAND Min: 200Mhz Max: 1000Mhz19 576
Tweaks: V6 SuperCharger : 3G TurboCharger : KickAss Kernel