Problem for Sony SDM-HS75/B (Black) 17" LCD Monitor Menu buttons don't work but menu randomly appears

Try this:

Under the menu options, there's Menu Lock. Switch it to "On". It worked for me.
My menu button wasn't working, so to access the menu, I had to hold down the arrow up button and push the arrow down button till I got to the Menu Lock Option.

The problem might be the menu button.

1. Try to press and hold down the menu button for 7 -10secs.