can't pan page without turning page

Don't know if this just happens in Chrome, but I can't seem to pan a zoomed page without turning the page (for example go to http://www.archive.org/stream/panamapacificint00moor#page/13/mode/2up and zoom in). Every once in a while it works, but most of the time, when I let up on the mouse button after a pan operation, it treats it as if I clicked on the page and therefore turns the page. Turning the page with just a click is convenient, but perhaps you could expose the option in the UI to turn it off (or perhaps use the spacebar instead). Again, didn't test this in other browsers - might be Chrome-only issue. Thanks.