imei 0049 but network registered

You didn't properly upgrade and downgrade...or maybe something went wrong during the process..Whenever you install a ROM you should always take a backup of your EFS partition in order to avoid such issues.I am sure the DITTO Rom installer must have generated a backup of the EFS while flashing/installing it ..if that is so you will find that in the internal SD card mostly. Secondly,I don't know about other but i have faced this issue with my Samsung Galaxy S2 ...Sometimes the IMEI is proper in the partition but it shows it to be wrong..and the network connects !....and the imei shows proper on restart / flashing other ROM...

This might help !...
1.Search for the EFS restore image created buy the ROM flasher..into ur Computer system
2.Follow this guide http://xdaforums.com/showthread.php?t=2088809 and check if the IMEI comes proper..if it doesnt then use the EFS backup to restore in that case refer this http://xdaforums.com/showthread.php?t=2255943

the network might evict you maybe later..or i dont know its wierd needs the attention of some person with more knowledge...