I have successfully hooked up my Gateway laptop to an RCA HD TV & an Insignia HD TV, but I can not get my 42" Westinghouse 1080p HD TV to work w/ laptop. I am using HDMI connection. I did get it to work for a few seconds, but never again. When I plug HDMI cord into other tvs I get a sound on the computer. No sound w/ Westinghouse TV. Any ideas?