Migrated from online 5 to online 7.1 now runs slow.

Hi. I don't know if anybody can help, I have just been contacted by a friend who unfortunately doesn't have access to this newsgroup. He is currently involved with a company who run a large suite of Informix 4gl programs. Up to about 8 weeks ago they were using Online vers 5 but have now upgraded to version 7.10. The users are now complaining of performance problems. Typically a report which took about 20 minutes to run is now taking somewhere near 4 hours. He has been called in to try and speed things up by modifying the code. He's a switched on guy and he's checked for all the usual things but can find very little wrong with the code. The company previously contacted Informix and one of their guys has been to look at the setup but could find nothing wrong and pointed the finger at the 4gl code. I've seen some references in this group to poor performance if version 7.1x online is used with code that has not been compiled by version 6 i4gl, maybe that's the problem.. The version numbers are as follows: Online vers 7.10D1, i4gl version 6.01UD2. If anybody can throw any light on the subject I would be pleased to hear and will pass it back up the line.. Dave Ingledew