I thought there was an option to limit the number of titles saved in the playlist. But looking at mine I can't find it. I know you can clear it by running regedit and deleting them, but don't mess with the registry unless you know what you are doing.
Hmm, I was pretty sure there was an option somewhere. What version are you using. I have 6.4 and can't find anything about clearing the playlist in the options tab.