Have you checked your c:>FeralHeart>Media>Particles folder for duplicates?
e.g} Smoke_0 and the numbers may increase. If there are duplicates simply delete them. {Be sure to ONLY delete the duplicates aka the particles ending in _0 _1 etc }
Since you're saying that you have to click 'Ok' in order to try getting ingame, then you must be seeing this:
(http://i.imgur.com/d5ILANG.png)
If so, then you can't change your rendering system between OpenGL and Direct3D9 the normal way, which is through Feral Heart's Options \\ Video. Instead, you will need to locate the ogre.cfg found in Local Disk (C:) \\ Feral Heart, and open that up with Notepad. Once you have done that, delete everything inside and replace it with the following code and then hit CTRL + S to save, or 'File' then 'Save' in order to save it:
Render System=Direct3D9 Rendering Subsystem
[Direct3D9 Rendering Subsystem]
Colour Depth=32
Display Frequency=N/A
FSAA=0
Full Screen=No
RTT Preferred Mode=FBO
VSync=No
VSync Interval=1
Video Mode=1280 x 800
sRGB Gamma Conversion=No
[Direct3D9 Rendering Subsystem]
Allow NVPerfHUD=No
FSAA=None
Floating-point mode=Fastest
Full Screen=No
VSync=No
Video Mode=800 x 600 @ 32-bit colour
sRGB Gamma Conversion=No
If that doesn't work, then you could always try removing duplicate particles ending in _0, _1, _2 (etc.) in Local Disk (C:) \\ Feral Heart \\ Media \\ Particles as people are suggesting, or this:
Right click the Feral Heart icon and select 'Properties'.
(http://i.imgur.com/cDyHloY.png)
Go to the 'Compatibility' tab and check the box next to 'Run this program in compatibility mode for' and select what you are currently using in the dropdown box. If you're unsure, then experiment with different ones.
(http://i.imgur.com/srvQydn.png)
The game works now, but whenever I log in, the area surrounding my character is pitch black and only my character shows, how would I fix this problem?
This post can fix your problem!
https://feral-heart.com/smf/index.php?topic=56857.0