twitterfeed update problems (although using delicious through yahoo pipes)

I'm feeding my Twitter account with my del.icio.us bookmarks via Yahoo Pipes. This solution seemed to work quite well until a few days ago. As a matter of fact twitterfeed keeps importing the rss entries of my delicious-through-yahoo-pipes rss feed over and over again. Thus every bookmark is being posted at least twice (or even more).

Any suggestions?

Edit: It seems as if shortening the URL using tweetburner is the problem. Actually I'd like to omit a switch to a different shortening service because I like the way I can keep track of my posted URLs using tweetburner.
 
sad I’m frustrated
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