mazda3uzr

I have a xbox and shuttle in my car which are powered through a 300w xantrex inverter. when the xbox was turned on, it use to make a very loud buzzing noise until i wrapped some solder around the rca grounds at my zux input adaptor which eliminated the noise. but now with my shuttle, everytime i plug it into the inverter, there is some kind of buzzing sound that sounds like morse code haha. then when i turn it on, there is a very buzzing sound. I also am getting these lines going up my lcd which i cant seem to get rid of. BTW, none of these problems exsist when everything is plugged into a regular wall outlet, and i am sure it is not the inverter because i have tried about 7 inverters and this is the best one yet. someone, please help!