Acrobat XI 11.0.0.7 on Mac renders 2 pages in a PDF incorrectly as blank. Any ideas to why?

Hi

We have a 26pp PDF document which when viewed in Acrobat XI 11.0.0.7 on OS X, 2 pages are rendered as blank in the main page view and the thumbnail view. All other pages render fine as do all other PDF documents. Viewing the same PDF document in Acrobat 10 and 9 on the same Mac shows both pages fine.

To add mystery to the scenario, the same 26pp PDF viewed in Acrobat XI 11.0.0.7 on two other Macs running OS X is all good and the two pages in question on the other Mac view fine.

Is there anything in particular that could cause this problem on the one Mac?

Thanks for your time.