Select hangs - Help!

Can anyone shed any light on the following problem. Twice over the past four weeks, one of our customers has reported that their entire suite of Informix 4GL application programs (developed and supported by us) suddenly hang. On further investigation I discovered that one table was causing the problem (although it was a different table on each occasion): if I attempted to select from the suspect table, the select would hang. Selecting from other tables worked fine. The reason why the customer reported that the whole suite of programs were hanging is because each program selects from both of these tables as part of the program initialization procedures. On rebooting the machine I checked for database corruptions using bcheck. There were none. I therefore conclude that it might be some sort of locking problem. However, both tables that were involved are rarely updated (and then only by hand - never by a batch job). As I have already suggested, they are read (selected) from a lot. To my knowledge no programs set the lock mode to wait. Has anyone else had any similar experiences? This particular customer has three sites networked with Informix-NET over TCP/IP. About 50 users log directly on to the server, and about 40 onto the remote sites. The server and one remote machine are ICL DRS6000's; the other remote machine is an ICL DRS500. Software versions are as follows: server (DRS6000): sqlexec: 4.00.UE1 sqlexecd: 4.00.UE1 operating system (DRS/NX): release 4 version 6.3.05 remote site 1 (DRS6000): sqlexec: 4.10.UC1 operating system (DRS/NX): release 4 version 6.3.05 remote site 2 (DRS500): sqlexec: 2.10.03K operating system (DRS/NX): release 2.22.03 version CF -- | Steve Chell steve@fujitsu.co.nz | | Fujitsu NZ Ltd PH: +64.9.3077930 | | Auckland, New Zealand FAX: +64.9.3562437 |