Is there a fix for iBooks being *extremely* slow once my ebook has highlights and notes?

My ebooks respond to gestures quickly in iBooks until I add highlights, notes, or other annotation. Then it takes10-20 seconds to do anything--turn a page, select a word, highlight new text, change the highlight color, etc. I use the latest iBooks release (1.5) with iPhone 3GS and iOS 5.0.1. Does anyone else have this problem and is there a fix? Thanks!