mini dvi to hdmi problems - displaying my screen on my TV

so I have an Toshiba LCD TV with an HDMI port and I'd like to be able to play videos from the internet on my TV. I have a Macbook with a mini-dvi port so I bought a mini-dvi to HDMI adapter from Amazon and an HDMI cable from Best Buy. I also have an RCA cable for audio (which works fine). After hooking up the laptop to the TV using a multitude of combinations and restarts, all I get is a flickering blue screen on my laptop when I change the TV's input to HDMI. Nothing happens on my TV screen. Any ideas on what I should do to get video? I've read I need to mirror the display but the Arrangements tab doesn't show up on the Display menu so that option doesn't seem to be available. I've messed with resolution and numerous other things and have hit a wall.

Help please!

Sorry, but have to ask - you are choosing the correct HDMI port?

First thing to do is unplug both adapter and cable and plug them back in even they look good.

I always hot plugged both of the Toshiba HDTV sets I've had. I kept the cable permanently attached to the TV, the Mac booted up, TV input already set to the correct input, then plug the cable into the Mac. You might give that a shot.

When you open up Displays preferences there should be two windows - one for the MB screen and one for the TV - you may need to move one window to see the other. Each one controls a single screen. I believe the Appearance tab will only be on the window for the TV.

Thanks for the reply!

As for your first question, there is only one HDMI port on my TV so I'm assuming I'm using the correct one.

I tried it on my mom's TV, which is also a Toshiba DVD combo but a little bigger. This time the first time I plugged it in the screen went blue and then came back on and the resolution changed. Then the mirror option turned on but still nothing showed up on the TV screen. So I clicked Detect Display and it just went back to the old resolution and the mirror thing went off. After this I tried again and the computer had no response...a couple of times the screen went blue and went back to the desktop but other than that, nothing.

So the Mac recognizes it's being detected in both cases - but nothing but a black screen on either of the TVs?

Are both of these sets over 4 years old? If not please provide model numbers. Many of the first couple of years models of HDTV sets just did not pass the proper info to computers - pretty much every manufacturer - no one was thinking about it. If you have the owners manuals still, I'd pull them out and do a little reading in the connections section - you'll be looking for anything referencing connecting a DVI device.