Hi Sharon,
No, I haven't had that specific problem, just a bunch of others. Looking at what you've already done, I think you need to have one of the dealers call Tin Lizzie (you can't do this yourself), and have them determine what chip or board they need to replace in your stitch regulator. I know it's a pain, but you probably need to take the machine to the dealer, since you've done all of their requests over the phone. Unless, you live close to your dealer and they do house calls. I've taken mine in several times and had to leave it in the shop.
I hope you get it resolved soon. I know how frustrating this must be for you.