bitvoicer home automation project problem

hello everyone,
I have a problem with bitvoicer. My current project is trying to control my desk lamp with bitvoicer(with arduino uno).
I succeed in controlling LEDs with bitvoicer but my problem is when i try to control my lamp(i connected the board to a relay directly, the relay to the lamp), bitvoicer freezes.
I think my program is fine because i copied it from the forum(led controlling program: Speech Recognition with BitVoicer, Arduino and a Microphone - Audio - Arduino Forum) and only added couple of lines for the relay:
int RELAY=2;
and couple of "if" arguments for turning it on and off.
Another fact that i didn't understand is that the lamp turns on and off, and the program in general works fine a couple of times before bitvoicer freezes.
When bitvoicer freezes i get the massage on the monitor:"error unable to open serial port". and when i unplug the board bitvoicer gets "unstuck".
could it be back emf or anything like that? because it only happens with the relay(by the way it works on 220v ac).
any comments would be very appreciated, and sorry for the bad grammar.