Informix Online Engine Dies Inexplicably

Every so often, our Informix 5.1 Engine on a Sunos 4.1.3 box dies for no apparent reason. Logs are not full, there are no problems reported in the log file. The last checkpoint will have occured hours ago and people will be able to start isql, sometimes even able to select data, but not leave isql. I wonder if anyone else has had similar problems and can shed some light? Tim Tim Helton timh@amgen.com Amgen doesn't believe a word I say, maybe they know something you don't?