Sudden Inappropriate Barking...HELP!

We have a 7 year old corgi/terrier mix who was abused by former owners and has a whole host of anxiety issues (we've had her 4 years). She had severe separation anxiety from my husband and used to pace all day, but we let her into the basement and "his" chair and then she slept there happily all day. She seemed so much better, happier, more playful, and no more anxiety. It was a huge relief. SIX MONTHS of good behavior.

Then, the barking started. She's always been a high-strung but not particularly barky dog. The past few weeks, though, she's started barking...

- when I walk across the floor
- when I open a door or cabinet
- when she hears me talking to the cats or my husband
- when my husband and/or I stand up from a seated position

Even though it's clear that it's ME and not a strange person, she'll give one or two sharp nervous barks. Doesn't sound like much, but if you add up all the little sharp barks, it accounts for a steady day of barking. I've tried ignoring her, I've tried telling her NO, I've tried sending her to the crate for a few minutes each time she does it. It seems like it's getting WORSE. Because of her former abuse, she's very resistant to any type of training (it's taken YEARS for her to learn 'sit'). My nerves are wearing thin and, of course, that exacerbates her anxiety.

What can we do?