Most of my stuff sounds fine, but I've got a handful of albums (The Gathering's Souvenirs and any post-metal Ulver) that have annoying-as-hell sibilance all over the place... even worse since all four of them are on the whole rather quiet. Here's a sample of a song from Ulver's Perdition City that's as good a snapshot as any:

http://s37.yousendit.com/d.aspx?id=2I41W8T...LS2BW56VZZP2SJA

Anybody know if there are any plugins or programs that can help remove that sort of thing? And, since I'm curious, why it happens in the first place? Thanks.

It's all due to the way it was recorded. You can use a limited to get rid of that -- there's a preset in adobe audition that allows you to treat those files quickly.

You can try a de-esser. I know a few (expensive) standalone boxes, but you might be able to find a plugin for your application.