E7 should be running symbian^3 ( with the nokia browser 7.2 ) or symbian anna (with nokia browser 7.3 )..thus info here
would be relevant..
and if it is 7.3 here
You could always sign up at nokia in their dev forum and ask them about it ..but given their tie-in with MS they might not give you an answer :)
Opera mini has always been weird about adsense delivery ..
Works in G mobile browser ( the android default version ) but does not direct one to the mobile version..I have noticed something in the code which might prevent some browsers showing the top banner..Opera does not show this on mobile..But as it involves "specifics" will send you a sticky..