Trouble with EndScene hook

[LdGn29]

I'm trying to install hook, but always game crashes with some weird exceptions

All what I do is:
1)Allocate memory
2)Write some instructions + first 5 bytes of EndScene + jmp back
3)Write jmp to allocated memory

Instructions:

string[] asm = new string[]
{
"pushfd",
"pushad",
"popad",
"popfd
}

(It is because earlier here was some logic that doesn't work)

Next I read first 5 bytes of EndScene and inject them after ASM bytecode:

Memory.Write(detourAddress + (uint)asmLength, Memory.Read(pEndScene, 5));

And then I write jump to (pEndScene + 5)

I write jump to my detour in pEndScene and game crashes with ACCESS_VIOLATION exception and gives me address of instruction at (pEndScene + 0xB)
I tried to fix that, swapped first 5 bytes of EndScene with my ASM bytecode, took 6 bytes and wrote jmp + nop, but it also gives exceptions
Last was also ACCESS_VIOLATION but now at (detourAddress + 0x76), although my code only 24-25 bytes length including jump back

Also in crash report I found that WoW uses D3D9 adapter.

What I did wrong?

[charles420]

suspend WoW main thread
-allocate memory for your codecave and copy all your code there
-alter EndScene memory page properties to be able to write at
-write jmp opcode at the beginning
-resume thread and probably set all changed properties back