For those of you who read what I wrote before, sorry to have deleted it. Much of what I put into the description of the problem turns out to be irrelevant to it. So let me rephrase completely.
I have turned a Memo control (ansistring) into a RichEdit. Plain text (record) is shown and can be edited so that it becomes rich text. Memo's are shown in a treeview, so clicking the memo in the treeview shows its content in a window next to it.
Now: the problem. Nothing is wrong when text is 'enriched' as long as the first letter is left alone. That is to say: if the first letter remains unedited, scrolling through the memo's shows no changes except for those in that one memo. If some part of the text was set to bold, it stays bold just where it was supposed to. However. If the first character is edited, say set to bold, then all other memo's immediately turn bold, as if the style for the whole application was supposed to be changed.
Previously I assumed this was related to stringstreams but it turns out not to be the case. Sorry for that.
I have used code that came with Delphi Studio 7, the RichEdit Demo, and put this into my own application that showed, as described, just plain text memo's in a treeview.