Error -565 in Informix Online WorkGroup Server 7.30

Error -565 in Informix Online WorkGroup Server 7.30 Windows NT Please help! While I am executing an Informix 4gl program the system gives me this error: SQL statement error number -565. Cannot read sorted rows. SYSTEM error number -172. ISAM error: Unexpected internal error -565 Cannot read sorted rows. This is an internal error reflecting an unexpected condition while performing a sort. Check the accompanying ISAM error code for more information. If the error recurs, please note all circumstances and contact the Informix Technical Support Department. -172 ISAM error: Unexpected internal error You encountered an unanticipated internal event. Consult the online.log to see if OnLine's diagnostics preserved any further information regarding this event. If the error recurs, please note all circumstances and contact the Informix Technical Support Department. I consulted the online.log an it's all OK. Only I usually saw this message but I don't know it's related whith my problem: 22:17:46 dynamically allocated new shared memory segment (size 8388608) The Informix Online is up 20 days and this problem only occurs the last three days. Miguel 'ngel Ferrer ma-ferrer.eos@ctv.es EOS Inform'tica