I had to read what you've been given for advice because my 1 year old is doing the exact same thing..
I dont understand the people suggesting the baby slings and such... my little one is 21 1/2 pounds... my back can only handle her for so long! lol
The only thing i've found to somewhat calm my own little one down is trying to do everything i can while sitting in the same room as her.. I give her some one on one play time on the floor for awhile, till she seems a little better, then gradualy move further away and keep where i can make eye contact and smile contact. i bring the laptop to the couch next to her, or a book or my lunch or whatever..
If i've tried everything and she's changed, fed, napped, etc, i try to ignore her fussing for a bit while i do whatever else while still sittin near her, looking at her occasionally and smiling. sometimes eventually she goes off to do her own thing, sometimes not.
Usually when she does the i want up, no i want down game, she's at the end of her rope tired.. then wont go down for her nap w/o a fight.. which i've started reading to her after puttin her in her crib and it seems to calm her to sleep about 80% of the time.
Maybe at this age they're just realizing the scarey fact that they can't always have what they want when they want it! And are just really mad at this new idea! :)
As mom's we want what's best for our little ones and would give anything to see them always happy. Unfortunately it just isnt' up to us!! ;)
Good Luck and Hang in there!