Faced a unique error with jQuery today. I was using jquery-1.3.2.min.js and jquery-simplelightbox.js. Which were included properly in the jsp file, but still the javascript was throwing the error that simpleLightbox function is not found.
on a close look it was found that after adding both the JS files, an additional jsp file was added which was again adding jquery-1.3.2.min.js, hence overriding the original jQuery object.
Lesson learnt- Always make sure that jQuery js file is added only once, especially if we are modifying the object.