ERROR: AV's and IWButton.picture.data: the parameter is incorrect

[MrSpock]

Sorry, a bit confused.. Is it still wrong even AFTER you moved everything to UserSession unit ?

You are correct.

I only could not move TIWImage to UserSession, as I had put it on the form at design time, and this may be the issue. I create forms using

procedure TIWForm2.napisLinkClick(Sender: TObject);
begin
  Release;
  TIWForm6.Create(WebApplication).Show;
end;

It seems that in this moment some form variables, I mean components, values are common for all users connected.

Again manual lacks proper description on how to cope with such basic problems. I feel like abandoning using intraweb.