rows are not refreshed properly in IE when $viewport.scrollTop is > 0

To reproduce:
1. use IE 7, 8 or 9 (I have not tested IE10)
2. go to http://ericmbarnard.github.com/KoGrid/#/examples
3. go to the Server-Side Paging example
4. scroll the grid content down to approx halfway
5. click filter and type in "505050505050505000"
6. The grid now says "Total Items: 1(Showing: 1)" but the rows are not visibile


Thanks very much!
Ted

Start with the Server-Side Paging example at the KoGrid examples page and reproduce the issue in IE 7, 8, or 9 after scrolling and filtering. Compare the grid's reported item count with the visible rows; done means the matching row is visible when the viewport is scrolled before filtering.

Written by the indexing model from the issue text.