OK, I did same as you guys, and applied the 4.09 server patch to a working 4.08 server, with same result....server is pooched.

I made a note of the four .dll that were replaced by the patch:

il2_core.dll
il2_corep4.dll
mg_snd.dll
mg_snd_sse.dll

and I replace those with the old ones from the working 4.08 server, and now it works!