I had noticed a considerable slowdown in this blog sometime ago and had not been able to track down the cause for this slowdown. I had tried a variety of different things including breaking down the database into small portions and the code into more sizeable chunks to try and isolate what was causing the slowdown (including all kinds of optimization/repair techniques).
I remembered this morning that I had installed Spam Karma to test it and had since uninstalled it. However, I had not realized that Spam Karma had created a fulltext index of the comments table and I had not removed that index. Adding to the problem was the feature of WordPress 1.5 that stores all spam comments. The comment fulltext index had grown to over 50 megs in size (with over 25000 spam comments plus the few thousand legit ones). All of this resulted in every mysql query taking more than one second to execute.
I removed the fulltext index, cleaned out all the spam comments and optimized all the tables and the speed seems to have returned. This post is not meant to defame Spam Karma since I believe that it is a VERY good plugin but it is meant to educate other users that might be having the same problem. If you want to continue using SK with WordPress 1.5 and want to recover some of the performance loss, I suggest you use some kind of a plugin that deletes spam comments instead of storing them in the database.