N64 MARIO CART freezing with 2 players

Okay we bought our 5 year old the original N64 for Christmas and it worked perfectly until last week. The only relevant part to explaining this is we moved the TV (thus the N64) to a different area in the house. Since doing this when we play Mario Cart (only with 2 players) it freezes about 2 boards in. The most bizarre part is we have replaced the system and the game and still have the same problem! It's mind boggling and highly frustrating to say the least. Any input would be so appreciated as I have googled like mad and can find no answers relating to this.

thanks so much!

Kate