1. Downloaded cm-10.1-20130128-NIGHTLY-i9100.zip and copied to internal SD. Verified MD5 checksum (2375030e0c9cf4299e4c0375970646d6).
2. Reboot into CWM Recovery.
3. Created backup.
4. Flashed cm-10.1-20130128-NIGHTLY-i9100.zip
5. wipe cache partition.