Wiring problem!!

Hi,
Last year we bought a 3 family home in mass,as rental property.
Last month I hired a contractor to re-build the 2 story front porch,wich was in bad shape.
They replaced the first floor porch ceiling light in the job.
The 1st floor tennant called me right after the job was done,saying the porch light didn't work,her TV blew out (19")
and two floor lamps in the same room blew the bulbs.plus the door bell was ringing for no reason!
I called the contractor to go find out what was wrong.They did,the got the light working,etc...
1 week later she calls again saying another TV blew out,wich is in her living room (the same room as the porch light switch).
Two Tv's have now blown out??
Any ideas?It was fine until the porch work was done?This living room,wich is affected is the first room off the porch...
Any help would be appreciated.The contractor says he has it wired the way it was,and there must be another problem?
Thanks

 

They put some nails or screws into the wiring.

 

An open in the Neutral of a 3-wire Branch-Circuit can result in 240 volts across 2 loads in series with un-equal voltage divisions across the loads, such as 200 volts across load A and 40 volts across load B.