Integration error when retreiving a sub opportunity from integration queue

Hi All,

 We have a java program that runs every two minutes and it goes and reads CRMOD integration queue, fetches data and writes it onto a staging table. We also have a workflow that triggers whenever a new opportunity is created or updated and send record into the integration queue. The program / code runs perfect if its a parent opportunity but throws this error when its a child or sub opportunity. Intresting part is that, if we create a sub opportunity from the Create opportunity button and then associate a parent opportunity record via lookup it works fine, but if