Its not the thread, its the machine. This may sound silly, but try re threading it and make sure you arent missing something. Mine was doing same thing then I discovered the thread wasnt in the takeup lever. Takes years and years for thread to rot. Think about all the antique quilts there are that are still in great condition. In passing, I will say that in my opinion, Coats and Clark is not good and even worse for your machine.

Have you consulted the sewing machine company. They may have a FAQ and talk with a local dealer about the problem.
Machines are different and just changing thread might not be the problem. there may be a problem in the machine.
Each situation is different and I find it more helpful to go to the source.

I find the new Coats and Clark is not satisfactory for me.
However, the older thread (before the change) works very well for both machine and hand work. That is why I buy all I can when I can find it, and I've found a lot lately.

I never thought it would be so difficult to sew on a NEW machine. I'm getting one for my daughter too (from her grandma) and I'm wondering if she won't want the same one I got after all this thread issue.....

I only use Guterman or Aufril in My Viking Sapphire

I mainly piece quilts with either Coats & Clark or Connecting Threads - thread and sometimes FMQ with it. I have no problems with either one.

I wish I was you. :)

Its time to adjust the tension ever so slightly a little at a time and use scrap the same thickness as what you are sewing. Sometimes a new machine is a little uptight!

you might want to also try a different SIZE needle and adjust your tension. accordingly. good luck. try a different thread if all else fails :-(

When I bought my Viking a few years ago I remember being told NOT to use Coats & Clarks thread, EVER. It is simply not made the way it used to be. I now use 40 or 60 wt. polyester embroidery thread. Isacord is my favorite for piecing and you can get the king spools online for about $7.00 for 5000 yds. It is strong and thin and makes for more accurate piecing and fewer bobbin changes.