After I had just gotten this ROM almost all set up the way I like it I ran into service troubles and the IMEI came up as unknown. I thought all the installing and uninstalling of apps (especially wi-fi hotspot stuff that was for ICS and FCing) must have hosed my EFS as I posted here: http://forum.xda-developers.com/show...2019540&page=2
After recovering my EFS I re-flashed back to this ROM and started setting up my apps. During install and config I popped an unknown IMEI again. I tried rebooting, pulling the battery, airplane mode on/off and the IMEI was still unknown. I hit the factory data reset just on a whim, and when the phone came back up the IMEI was ok again!
I ran an EFS backup, and a CWM backup and started installing everything again. Same as before, when I had the majority of my stuff installed the IMEI came up unknown. I now figure that the EFS must not actually have been corrupted (so I went through all that backup, change and fix IMEI crap for three days just to prove it can be done on our phones!) I rebooted into CWM and deleted dalvik cache and on reboot the IMEI is back! This happened one more time while transferring things and fine tuning settings. After a reboot it came up unknown, I wiped dalvik and reset permissions and it came back to life. It happened again, and trying the wipe didn't work. Factory data reset worked, then ran a CWM restore.
I have never had problems with this phone before, and have only been running custom ROMs for a long time. I wonder if there is a bug that is causing the OS to be unable to read the IMEI even though it's not actually corrupted? Maybe this is just isolated to me?