RE: Omega Steam Cleaner SC104 - can't get top off to fill with water -?

I got an Omega hand-held Steam Cleaner SC104 at a yardsale, too, and couldn't get the top off. I followed Mark's suggestion of November 2010 and got as far as getting water through the little hole in the top and plugging it in to make steam. No steam came out, so the nozzle must be plugged. I tried turing the cap when it cooled down a bit and it seemed to be unscrewing. I kept turning and turning till I realized the hard rubber had softened and lost its grip on the brass screw top. The rubber cap came off completely and the screw top is still stuck. What is CLR Calcium Lime Rust remover? Will white vinegar work?