Ok, I've managed to have a bit of a play around and had a bit of a look into the plugin you are using. Two things,
- This plugin has the worst documentation ever. I'm talking, they don't even explain how to get it working. I did exactly as they said and it didn't work, additional markup was required which I was able to grab from the demo which was not mentioned anywhere.
- I don't think it supports multiple scrollbars. I know, I know, the documentation hints that it does but refer to point 1. The javascript only seems to be able to interact with one of the scrollbar divs. (this was one of the divs not mentioned in the documentation)
I honestly don't have much time to really look into it deeply sorry, but I've tried a few examples from scratch and the moment a second scrollbar is implemented it doesn't work. Perfect example:
my latest playaround. I set up two idential divs - every id simply appended with a "2". I've commented out the JS to initialize the first block of images so only the second is currently executed. You can cleary see it simply ignores the second scroll bar and uses the first scrollbar to control the second block of images.
A little confusing there, but if you jump in and play around you'll see what I mean. Bit of a shame really because it looks and seems to work nicely although I imagine it would look like ass in older browsers.