I have the following problem and it has cost me already a lot of hairpulling, so I thought I'd share the problem with you. I've come across two different example sites where #1 also has the problem, but #2 doesn't.
1. If you go to a example page (on desktop) of popups with Openlayers: http://jorix.github.com/OL-FeaturePopups/examples/feature-popups.html , You will see that when you click the marker in India, a popup will open with a scrollbar and you are able to scroll the content. When navigating this site with a tablet or phone, you're not able to scroll / swipe / drag within the popup.
2. I you visit the site http://openlayers.org/dev/examples/getfeatureinfo-popup.html (desktop) and click on the blue area in the bottom of the map, you also see a scrollbar and are able to scroll. When navigating this page with tablet or mobile phone, scrolling the popup DOES work.
I experience the same problems on my site as #1, but am unable to fix it. I've copied styles etc. from the second example, but to no avail.
Anyone else has this problem?