tcpip streams SCO OS 5.02 & Informix 7.2

I have a problem with streams allocation on SCO OS 5.02. I am running SCO & Informix 7.22 on a 4 CPU Compaq ProLiant with 512 MB RAM. Connections are mostly across TCP-IP using Informix Cient on WFW.311 (I-Net 5.1) max 25 users) & NT 4 (CLI 2.5) (max 6 sessions). There are half-a-dozen connections via X-Vision vt220 Terminals from NT WS's. What appears to happen is that connections are made, but the stream resources are never de-allocated. When the stream usage exceeds the allocation, tcpip 'freezes', all connected sessions lock up and no one can get to the system other than on the console. Initially, there was 2MB allocated to tcpip streams, this was doubled to 4MB, then to 8MB, and now to 12MB - which seems to be as high as I can get it. I have ensured that the latest Client releases from Informix are installed. I have tried running with all NT servers & workstations switched off (then usage still grows, at a slower rate, even with nobody accessing the system from WFW PC's). I am preparing to upgrade to Informix 7.23 & SCO OS 5.04. Has anyone ever come across this before & found a solution, only I'm not clear the upgrades will make any difference. Terry O'B