1 Create document with more 60 formatted headers 
  ("Heading 1" in my example).
2 Format it as two column layout.
3 Insert "Table of Contents" on second document line:
  document looks good, all pages have two column.
4 Save document as .doc and close it.
5 Open document:
  now "Table of Contents" has only one column while rest contents has two.
  It's formatting is damage.

6 Open Format/Page. 
  You find 1 instead 2 in the Columns field.
  Document structure has strange change.

Saving to .odt has no this problem.