I can create a new page in a SharePoint 2010 publishing site by going Site Actions > New Page. The Create page shows as expected. But when I try creating a new page from a pages library by going to the ribbon > Documents > New Document > Content Page, I get directed to the "Upload Document" screen instead of the create page screen. The page is a custom content type. I have checked the the Document Template for the content type is set to /_layouts/CreatePage.aspx but this doesn't seem to make a difference.
well there may be the issue the custom content type you associated with page library .
you have to inherit the content type from Article Page the Ctype of Article Page is 0x010100C568DB52D9D0A14D9B2FDCC96666E9F2007948130EC3DB064584E219954237AF3900242457EFB8B24247815D688C526CD44D
hope this will solve your problem