attachment zul file duplicate the problem
== Env ==
ZK : 5.0.4
Build : 2010090213
config in zk.xml
If remove the html tag (only simple grid) , it works fine
Rows height is not stable until after onRender.(Was calculated on onSize and usually larger than real number). That cause the engine to think the row is still visible and not loading.
Fixed since Oct. 6, 2010.