I use compilator MSVC6 and OS Windows 2000.
First of all I have tried to write fix for Win32Edit::setReadOnly because, when in code calls of Win32Edit::setReadOnly are repeated, then error of "Access Violation" occured because richEditCallback_ value after delete was not set to NULL.
So after first fix method look like this:

But this does not resolved all problems.
Next problem: when I repeatedly called this method, exception from Win32 RichEdit was throwed.
So I started to read MSDN about using of RichEdit.
In page http://msdn2.microsoft.com/en-us/library/ms652181.aspx I found solution or it is looked like solution because this does not worked.
As I founded later, meaning of params was wrong:
E.g. In truth lParam Specifies the operation, which can be one of these values, not vice versa, when wParam Specifies the operation.

So final solution looks something like this: