Simultaneous DBLOAD and LOAD problems

We ran into an interesting problem while testing our new AT&T 3555 with Informix this past week. We have established parent-child (RI) relationships with several tables and a parent table. When we run multiple (read'2 or more') loads or dbloads at the same time and both of the tables we are loading have RI relationships to the same parent table one of the loads fails due to locking problems on the parent. I though this was kind of interesting and was wondering whether anyone has a workaround for it (other than running our loads in sequence). FYI--this is a 5.01 environment but I believe someone mentioned to me they'd had the same result in 6.0. Thanks & Regards...Marc Baime