unable to view transparency in acrobat XI but able to view them in acrobat X

when i open certain PDFs with transparencies/gradients in acrobat XI, they appear white, but appear as they're supposed to in acrobat X.
i tried preferences/accessibility/replace document colors. Also, preferences/page display/show transparency grid and both didn't work. The preferences for both acrobat X and XI are identical (unless i missed something). Any solutions?