Comments doesn’t work anymore

Hi

I’ve been using WordPress 1.5, and have lately upgrated to version 2.0.

The upgrade went without problems, as I did what I was told ??

I have installed some plugins.

Already with v. 1.5:
– Adsense-Deluxe
– Counterize
– Search Hilite

And lately with v. 2.0:
– CaptCha!
– del.icio.us – Bookmark this!
– WP-Amazon

Yesterday I found out that you cannot comment on my posts anymore. What happens is that somebody posts a comment, but it isn’t send. And when they try to post again, they get a message saying “Duplicate comment detected; it looks as though you’ve already said that!”

I thought that CaptCha! was to blame, and desactivated the plugin, but it hasn’t helped. (So I reactivated it.)

I’ve searched here and on google to see if anybody else had experienced the same, but found nothing.

Do anybody have an idea about what is wrong here? And how I can correct the error?

My blog (in Danish) is on https://www.tips-og-tricks.com/blog

—
Kind regards
Britt Malka