1. Contact Mr.qbanin (search him @ samdroid or just search about the restore IMEI HOW TO), he can help you create the fixed nv_data.bin
2. pls follow the Tutorial here then i think you good to go:
Hi, I read your message about imei loss in i5800. I have the same problem, but I havent' the backup.
I dont' understand very well How Can I solve this situation.
I have adb shell correctly installed and a rooted phone.
Thanks in advance.