so....as the title says...how does one get out of a plateau?I've been stuck at the same rating for a good 18 months (maybe even slightly more...I'm not sure).

I do tactics everyday...analyze some of my opening mistakes with computer (Chessmaster....I know it's not the best...but at my level...does it really make a difference?) but nothing seems to work.

some advice would be appreciated

Maybe you could try to analyze a few long games with a coach. He could help you pinpoint your main weaknesses and how to get rid of them.

If you can't afford a coach, try to answer the question : what kind of mistakes am I doing repeatedly to lose my games ?

Maybe you should accept the fact that you've reached what seems to be your level. I've been playing chess for almost 40 years now (as you can see the photo is not me, but my son...) and at a certain point I had to admit that my OTB-rating didn't go up anymore. So keep playing the game, enjoy your successes, try to learn something from your losses but don't have the illusion that you can raise your rating to a much higher level.

Improvement isn't in a straight line, and there is no reason to expect it to be.  Plateaus are natural and happen at any level.

When you find yourself stuck, try taking a few days off from chess completely.  Then when you return, work on an aspect of your game you haven't been working on - do something different.  Change your routine.  Adopt a different style intentionally.

Compare it to running marathons... You might be doing your first one in 4 hours. After harsh training the second will be in 3h30. Then you might be improving to, let's say 3h15. But after that you will notice that progress is slowing down and in the end you will see that e.g. 2h50 is your limit, no matter how hard you keep training...

I don't beleive you. The photo must be you

Why don't you believe me? But anyhow: thanks for the compliment. I wish I would look so young...

chess videos help me a ton.  i learn better by watching and listening than i do by going over long, drawn out variations from a chess book, although i do that, too. 

http://www.associatedcontent.com/article/904029/chess_video_lectures_are_they_for_you.html?cat=19