House registration delayed

Hi, I have purchased an independent row house in bangalore in the year 2010. The sale deed was done in the year 2010 between the builder and me. The house construction got completed in 2012 July. But the builder has not done the registration of the house. The builder has some issues with the landlord of the property (builder has not paid all the money to landlord) and as a result the landlord is not agreeing to sign for the registration. Like me there are 5 other house owners for whom its the same situation. Though i have been following up constantly with the builder, its not moving forward and the builder is giving false promises everytime. I'm now worried how to get the registration done. In between some times the landlord is coming and asking to give rent to him since the house is not registered and the land lord is saying he has revoked the power of attorney to sale from the builder and made a gift deed of these plots to his son's name. Not sure what are the implications it can have. Can the landlord legally ask us to vacate the house. Since we have the legal sale deed and bank has also provided loan for the property. Can i file a case against the builder and put a notice to landlord of harassing us since we don't deal with the landlord directly. Need your insights what are the steps i should take to get the registration done.