运行起来时，好好地但是一操作频繁就会出现 could not load an entity

NHibernate版本为3.2.0.4000

有时还会出现加载不上hbm.xml问题，但是web程序多刷新几次就好了，这个问题是怎么回事？

could not load an entity: [Jump.Entity.Entity.UnitRoad#7b1f4d85-0a6e-4666-9d2b-9d7b48f7d41a][SQL: SELECT unitroad0_.UnitRoadId as UnitRoadId0_0_, unitroad0_.Version as Version0_0_, unitroad0_.CurrentApplyForJob as CurrentA3_0_0_, unitroad0_.Name as Name0_0_, unitroad0_.Status as Status0_0_, unitroad0_.Sort as Sort0_0_, unitroad0_.CurrentApplyPost as CurrentA7_0_0_, unitroad0_.ApprovedPositions as Approved8_0_0_, unitroad0_.FieldAreaId as FieldAre9_0_0_ FROM UnitRoad unitroad0_ WHERE unitroad0_.UnitRoadId=?]