It definitely happened after a reset and I'm fairly sure that when I tried it nothing else was running (plc's, motion progs, etc). In fact it was ater a reset and loading the config file that I first noticed the problem, because the config should have set I900=7. We also verified that the link settings are as they should be.
Are there any settings that might cause this problem that I could have a look at next time I'm on site?