Has anyone had any experience with a very annoying error "Internal Program Error 1621.K.No.ar " that continues to plague me every time I try to duplicate a page?

I'm nearing the end of developing the site and this recent annoyance is driving me mad. I have to close Xara, re-open it and then I can duplicate a page. It's happening at around page 134 and as I said,...I can't understand why this would start up all of a sudden and continue to haunt me as I try to finish this site up.

Thanks for any help that anyone can offer here.