Default [Q] IMEI number unknown S5830i

I recently installed cyanogen mod7 from Bieltv for my device gt-s5830i.
Installation done:

After installation everything works perfectly except the network related features.
Later i found out that the IMEI number is shown as UNKNOWN in my phone.
Typing *#06# displays nothing.

As suggested by various similar posts i installed galaxy toolbox. The imei number is shown in the toolbox also i could take bcup. However restoring that does NOT solve the problem.
Even seeing the backup in the hex editor the imei number shows up.

PS: My efs folder when viewed is shown as empty. Even with su permissions.
What can i do to solve the problem.