Something strange just happened. I commented on these WPs:

http://technology.desktopnexus.com/wallpaper/208366
http://technology.desktopnexus.com/wallpaper/208367

But the comments don't show! I tried to comment again and the same result. Nothing. No comment.

Though now it says: "Whoops, you've already posted that! (double-post?)". But still it doesn't show anything.

If it helps, I have Firefox 3.5.4 and Windows XP Pro SP2.

OK, this is strange agian. I just follow one of the links above. Now it shows a comment. But the other WP still ain't got anything. And yeah, on that WP where is shows now. Which is this one: http://technology.desktopnexus.com/wallpaper/208366
I refreshed multiple times before but it only just yet came.

Oh, they are all there now. Something seem to lag...

There was a delay with our caching system (memcached). I just tweaked the comment posting code to make the cache flushing a bit more aggressive.

Did this fix the issue?

Yes, it seems. No lag anymore. Thanks!