“Hi everyone,
Thanks for reporting this. Unfortunately, this is a known issue that has been plaguing us for some time. The problem occurs when you've created, deleted, and recreated a very large number of tags. We've been trying for some time to find a fix that'll work for the majority of users without impacting performance but so far we don't have a concrete ETA for having the problem solved. I apologize for the inconvenience and we'll continue to search for a satisfactory workaround in the meantime. Thanks for your vigilant bug reporting and for your patience.”
The answer is Bloglines.