.chm file display problem

Hi, heeeeelp.... Typical Microsoft help files (.chm type) displays incoretly, i.e. the left size with "content ", "index" ... tabs looks and works as usual, but right window shows nothing by clicking on topics (even there is no "window" as such, only white blank) I think, that some component of windows is missing or was deleted. What could it be ? I converted a few of those into .pdf files and content shows corretly.