You must have rooted device.
Then open root explorer go to system/app delete vending.apk then install signed version restart. Then Open titanium backup select play store wipe data. Open play store enjoy.
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Re: Google Play Store (Android Market) v3.5.19 + Modded
Use root explorer to move Vending.apk to SD Card incase anything goes wrong..... vending.apk is located here:- system/app/
install tha signed version, open root explorer den goto data/app & copy com.android.vending.apk to system/data, rename to vending.apk, make sure tha permission is rwxrxxrxx...... restart & enjoy guys!!!!!