I deleted a dupe post last night, from this thread... I just got a link removal request - from a spammer...
I believe that's the one you're talking about.
What happens is that the forum database periodically needs to be reindexed. If we don't catch it often enough, the forum can get very sluggish. cgi actions during this sluggish period can take forever, and if you hit "Submit" multiple times, which is the temptation while you're waiting, you will get multiple posts.
As phranque suggests, when this does happen, or when you see a dupe, it would help us a lot if you used the "report msg" link to the left of the post. Ditto regarding other discussion problems on the thread.