I think I have an idea as to what could be wrong. The content that I've gathered for the server seems to be working fine, yet whenever I try to join the server with the content that I have, particularly the Foliage pack, gives me a crap ton of eroded Lua. It IS possible that the content server-side is outdated, rather than client-side. If any admin can get to check this out, it'd be great. If this is not the problem, however, then take a look at this
video and follow it's instructions. It hasn't worked for me, so far. But it might work for you.
In the mean time I will continue and bash my head against my training equ-- Ah, Garry's Mod just updated. Could it be?
Edit: No, Garry is still a lazy fuck. Anyway, I think I know. This is the actual error from the script that I get:
[ERROR] addons/adv duplicator/lua/autorun/shared/dupeshare.lua:11: Module not found!
1. require - [C]:-1
2. unknown - addons/adv duplicator/lua/autorun/shared/dupeshare.lua:11
3. include - [C]:-1
4. unknown - addons/adv duplicator/lua/autorun/client/cl_advdupe.lua:5
This might be the problem for you as well. Try and find the problem that you have and either delete them, or, I suppse, try and add the file to your folder? I have no idea on that regard. It seems, though, that I'm missing it.