Metamod is loading fine my my Windows server, its SM that's borking out on me.
Here's the official communication I got from NFO
Re: L4D2 update and Sourcemod
Jul 02 2013 03:44
8 PM PT We found a workaround for the crashing problems caused by today's L4D2 update on Windows and we are applying it to all of those servers now. We also noticed that Sourcemod does not work with this update (even its latest snapshot), and we have renamed the left4dead2/addons/metamod/sourcemod.vdf file to left4dead2/addons/metamod/sourcemod.vdf.disabled on all servers that are running it, in order to temporarily disable it. When a new version of Sourcemod is released, we recommend using the Autoinstaller to upgrade, which will put the file back as well as update your SM install.