One of my clients has come back to me with a strange occurrence. When they created a new web part page, the Quick Launch Links were no where to be found. One thing that I noticed is that my heavily customized sites did not have this problem, but the sites where the master page was left alone, for the most part, seemed to have this issue. After some quick Google searching I quickly found the answer to the problem on two different blogs.
Making the Quick Launch appear again on Web Part pages stored in a document library – from Patrick Tisseghem’s Blog and No Left Navigation when new web part pages are created in sharepoint – from Patrick O. Ige’s blog.
I tried their fix and voila the Quick Launch Links reappeared. Long story short, I took the Quick Launch Nav out of the PlaceHolderLeftNav content place holder and it worked.
I suggest that you read their blog posts for the technical explanation.