This post should help get some of those mods that stopped working with the recent Half-Life 2 and Episode One update, working again.
1. Does the mod run on HL2 (SteamAppId 220)?
If yes go to 2. If not stop. The game does not need patching.
2. Does the mod have its own custom scenes (is there a scenes folder)?
Does the game have its own libraries (client/server dlls) (is there a bin folder)?
If yes to either or both go to 3. If not the mod will probably run without patching.
3. Change the gameinfo.txt file as follows:
4. Extract the scenes folder from the half-life 2 content.gcf and copy this to the mod’s scenes directory.
I would like to thank Peter AKA fitzroy_doll for writing and clarifying the above.
Gorpie is testing all the mods individually and is updating a thread on the Steam Forums.