I have entered my wallet code incorrectly 3 times and now it shows "Wallet Blocked". What do I need to do to unblock it ?

You need to wait; from the 6630 User's Guide: "If you enter the wallet code incorrectly on three consecutive occasions, the wallet application is blocked for five minutes. The block time increases if further incorrect wallet codes are entered."

See also "Resetting the wallet and wallet code" in the 6630 User's Guide.