problems with Ext.grid.plugin.BufferedRenderer

Hi there i have some caching problems with "Ext.grid.plugin.BufferedRenderer"

i have tried to empty the store in a grid panel with 30k rows and afterwords the rows cached by the plugin is not removed

When i scrool past the cached rows nothing is there as expected

Så my question is "how do i clear the cached rows by the bufferedRenderer plugin??"

for refrence i am using extjs 4.2.2

problems with Ext.grid.plugin.BufferedRenderer