it's so stressful when they won't sleep!

We've been through a variety of sleep dramas with our DD, so I'm always on the lookout for solutions. We've had similar to what you're describing, and took her out of the room and started again half an hour or so later with more success. With hindsight it's usually been related to teething or sickness or too much activity right before bedtime etc.

I've just been reading the no cry sleep solution for toddlers, which I'd highly recommend, and there are a number of changes I'm planning to make soon, primarily based around no longer feeding to sleep, which may be worth looking at. I expect it might be harder for a little while but hopefully easier in the long run.

Good luck with it!