I have experienced for first time ever, and in this server with the map rp_c18_v1 that the lightning is too dark than normal - Not like the screenshot of the posted map for download, but REALLY dark. This is a preview of what I mean:

http://cl.ly/0k0p3M2r3D3105241S2T

I meet all requirements and as said before never experienced this issue before. I run with these specs:

Apple MacBook Pro 15"
Intel Core i5 (2.4 GHz)
4GB DDR3 RAM
NVIDIA GeForce GT 330M

Note: Mac OS X does only support OpenGL as graphic engine, not DirectX. Therefore I don't have support for HDR in Source games.

What I've tried:
- Restarted Steam
- Restarted Computer
- Checked for updates (I have the newest updates for drivers)
- Checked other maps - Works fine
- Changed graphic settings.

Now what could be the issue, and if you have experienced the same issue please tell and if you have a fix, post it as well.

Thanks in advance.

Edit:
Note that this is AFTER the newest update of Garry's Mod on April 16, 2011

UPDATE: Maps works fine when I play it in single-player mode. But not in Catalyst Gaming's server.