Threaded View Vs Flat View

I've just installed a new computer and when I view postings here I have to click on flat view to see the whole of the thread. When I close the thread it reverts to threaded view. It never used to do this before and I can't see a way to get around it, although I'm obviously missing something which must be obvious. Anyone help? J.

Another thing has just become apparent.  I select the yellow colour scheme, but when I open and then close a post the colour reverts blue.  I guess ths must be something to do with the new PC, but I can't figure out why?