If you ever have a document with huge chunks of repeated text that you need to delete, just use the search and replace function (Crtl + H) to replace this text with nothing.  Just copy the "offending" text into the "Find" field and leave the "Replace" field blank.

This can be useful for removing all sorts of things.  For example, when pasting from older versions of Netscape, the result was that you often carried blocks of spaces into the final document.  This would delete most of that.  Similarly, I have used it to replace chunks of HTML code (e.g., "</b>") that sometimes show up in my documents as well as removing the numbers from numbered lists.

Note that you should take care to ensure that you are not going to delete any text that you *do* want to keep.