Access Violation in TWPRTFTextPaint.SetGlobalVar

procedure TLetterFacilitator.GetAsmtText( var LetterRichText: TWPRichText; var TempRichText: TWPRichText;
                                              sShortcut, sContentOwner: string; rAsmtID: double);
const
  MFL_ANSWER_TAG = '{A:';
  MFL_RANGE_TAG  = '{R:';


  procedure InsertResponseText(sRespTag: string);
  var
    i, iLen, sPos: integer;
    bStringFound: boolean;
    iTagLength: integer;
    s1, sID: string;
    sRespText: string;
    bGood: boolean;


  begin
    iLen := Length(TempRichText.AsString);
    TempRichText.Finder.ToStart;
    bStringFound := TempRichText.Finder.Next(sRespTag);
    TempRichText.CPPosition := TempRichText.Finder.FoundPosition;
    sPos := TempRichText.CPPosition;


    // loop through text until no more asmt text mfl are found
    iTagLength := Length(sRespTag);
    while bStringFound and (sPos < iLen) do
    begin
      // find position of end of current mfl
      if TempRichText.Finder.Next('}') then
      begin
        TempRichText.CPPosition := TempRichText.Finder.FoundPosition;
        i := TempRichText.CPPosition - sPos + 1;
        TempRichText.SetSelPosLen(sPos, i);


        // extract the response ID and remove the tag
        s1 := TempRichText.SelText;
        sID := Copy(s1, iTagLength + 1, Length(s1) - iTagLength - 1);
        TempRichText.SelText := '';


[color=red]<<----- ACCESS VIOLATION HAPPENS HERE (at least some of the time)[/color]


        try
           -- lots of logic stuff here


            if sRespText = '' then
            begin
              // delete mfl paragraph if empty
              TempRichText.FastDeleteParagraph;
            end else
            begin
              if sRespTag = MFL_RANGE_TAG then
              begin
                // a range tag - see if the response matches the specified range values
                try
                -- more logic stuff here


                    if bGood then
                    begin
                      // response matches range, include in text
                      TempRichText.SelectionAsString := sRespText;
                    end else
                    begin
                      // response does not fit range, delete response paragraph
                      TempRichText.FastDeleteParagraph;
                    end;
                except
                  // delete mfl paragraph if empty
                  TempRichText.FastDeleteParagraph;
                end;
              end else
              begin
                // an answer tag - just use the response text
                TempRichText.SelectionAsString := sRespText;
              end;
            end;
        except
          // not a valid number - no value to insert
          TempRichText.FastDeleteParagraph;
        end;
      end;


      // reset the length, to take into account any changes
      iLen := Length(TempRichText.AsString);


      // the finder's position must be reset
      TempRichText.Finder.Position := TempRichText.SelStart;


      // Find the position of the next occurence of a resp tag
      bStringFound := TempRichText.Finder.Next(sRespTag);
      TempRichText.CPPosition := TempRichText.Finder.FoundPosition;
      sPos := TempRichText.CPPosition;
    end;  // while bStringFound and (st < iLen)
  end;


begin  // body of GetAsmtText


  LetterRichText.ReadOnly := false;
  try
    // get the entire shortcut text - this may or may not have asmt mfl fields inserted in it
      PopulateBlobWpRtf2(TempRichText, 'HCC_LETTER_ANSWER_MFL_PAGE', 'LETTER_TEXT', 'SHORTCUT', sShortcut, 'CONTENT_OWNER', sContentOwner);


      // now find any embedded mfl fields and insert asmt data - check for answer flags and then range flags
      InsertResponseText(MFL_ANSWER_TAG);
      InsertResponseText(MFL_RANGE_TAG);


      LetterRichText.SelectionAsString := TempRichText.AsString;
    end else
    begin
      LetterRichText.SelectionAsString := '';
    end;
  finally
    // reset letter back to readonly and free memory
    LetterRichText.ReadOnly := true;
  end;
end;