Hi- I had this same problem when ebay made us take insurance blurb. I worked many hours trying to get this to work, send numerous support requests, WHICH I would suggest you do, keep pushing, send them some so they can physically check it themselves. At least you will know if it is possible if they try it.
I was told it was formatting issue with MY HTML. Would not change through auctiva or ebay. You may also be told that you can't cut and paste from works/word.. but need to do from notepad. I always did from notepad and had this problem.
I know you do not want to hear this.. but I had to go in and change each listing individually to take out the insurance blurb it took weeks to do this.
Good luck.. and I do hope you get it to work. . as I nearly pulled my hair out for days on auctiva support for a fix and finally just changed them all myself which took WEEKS and WEEKS.