[Action-N]

Hi I did find some things to comment on. First your header background image is to short an repeats. So I recommend using css to make it one line across. Or edit your logo to go straight across. There's alot of wasted space on the header now, shorter logo, less padding on the navigation, an I might see some forums without scrolling.
Also the rounded corners that big don't look right, an your collapse buttons aren't inside them.
On the thread page the thread title bar has rounded corners right on top of another bar an doesn't look right either. The thread text doesn't have any padding an touches the left table border.
On your post page the border around the date is pushing the table over an outside the lines on the right. I had fun with this issue on my styles, had to set a fixed width minus the border pixels so the table fit without pushing.

One last thing you used grays in the navigation, but nowhere else. The maroon pretty dominate so I think you should work the gray in further around the design.

I hope you find these helpful an don't take offense. Your site looks like it's booming an has great potential.