Click scrollbar's square (at the ends) and move mouse out (without releasing the mouse),
then move it back in, the scrollbar's square doesn't work anymore.
<zk>
<grid height="500px" width="300px">
<custom-attributes org.zkoss.zul.grid.rod="true" />
<rows>
<zscript>
Object o = new Object[100];
</zscript>
<row forEach="${o}">
<label value="x"></label>
y
</row>
</rows>
</grid>
</zk>

note1: when we move the mouse out, even it is loading data (ROD), it should still work after we move the mouse back in.

note2: This issue is inconsistent with different browsers.
Please reproduce it with Chrome and test against all browsers after it's fixed as it seems to be related to browser.