simple window crushes

hi to all
I'm newbie in FASM (yesterday migrated from MASM because I want to study OpenGL, but in MASM it's very uncomfortable)

but when I'm trying to create simples window, my program crushes! Sad

maybe I make some mistakes in FASM-specific syntax?? please, give me advice

here's my program, where's error??

Code:

format PE GUI 4.0
entry start
      include 'include\win32a.inc'

        section '.data' data readable writeable
          hwnd   dd   ?
          hInst  dd   ?

          wc    WNDCLASSEX
          msg   MSG

          szClassName   db   'newclass', 00
          szAppName     db   'FASM', 00

        section '.code' code readable executable
start:
          xor eax, eax
          invoke GetModuleHandle, eax
          mov [hInst],eax
          mov [wc.hInstance], eax
          xor eax, eax
          invoke LoadIcon, eax, IDI_WARNING
          mov [wc.hIcon], eax
          xor eax, eax
          invoke LoadCursor, eax, IDC_HELP
          mov [wc.hCursor], eax
          mov [wc.style], CS_OWNDC
          xor eax, eax
          mov [wc.lpfnWndProc],WinProc
          mov [wc.cbClsExtra], eax
          mov [wc.cbWndExtra], eax
          mov [wc.hbrBackground], COLOR_WINDOW + 01
          mov [wc.lpszMenuName], eax
          mov [wc.lpszClassName], szClassName
          invoke RegisterClassEx, wc

          xor eax, eax
          invoke CreateWindowEx, eax, szClassName, szAppName, WS_VISIBLE or WS_OVERLAPPEDWINDOW or WS_CLIPCHILDREN or\
                                 WS_CLIPSIBLINGS, eax, eax, 800, 600, eax, eax, [hInst], eax
          mov [hwnd], eax

msg_loop:
          xor eax, eax
          invoke GetMessage, msg, eax, eax, eax
          test eax,eax
            jz end_loop
          invoke TranslateMessage, msg
          invoke DispatchMessage, msg
            jmp msg_loop
end_loop:
          invoke ExitProcess, [msg.wParam]


proc WinProc, wnd,wmsg,wparam,lparam
        push    ebx esi edi
        cmp     [wmsg], WM_DESTROY
        je      wmDestroy
  defwndproc:
        invoke  DefWindowProc,[wnd],[wmsg],[wparam],[lparam]
        jmp     finish
  wmDestroy:
        invoke  PostQuitMessage,00
        xor     eax,eax
  finish:
        pop     edi esi ebx
          ret
    endp

         ;....
        ;import DLLs...

and even this useless program crushes with reason:

The instruction at 0x0006FE1B referenced memory at 0x0000003A. The memory cpuld not be "written".

Sad