The two screenshots displayed here are taken on the same machine (13" MacBook Air on OS X 10.7.3) and same browser (Safari 5.1.3). The ONLY difference is, the one above was taken while logged on to my home network, and the one below was taken while logged on to the network at the office.
As you can see, the one below is displaying scrollbars. Changing the window sizes makes absolutely no difference. The CSS is specifying a max-height and overflow:scroll for each of the DIVs. On the home network it behaves as expected, only briefly showing the scroll bars when you, ahem, scroll, then they disappear. On an iOS device, regardless of what type of network connection it works beautifully, never showing scrollbars at all.
I get that the scrollbars will appear on other browsers like Chrome, Firefox and the dreaded IE at this time, but this behavior in Safari is puzzling. Why does the same browser display 2 different results? The network factor is the only difference I can think of. I've tested this a couple times in the past few days, and the results are the same.