Cannot login

Hi everybody, we have encountered a problem with our Informix-Server: Sometimes ist is impossible to connect to the server via TCP-connection. To be more specific, it appears as connections become impossible when a certain limit of connections (in total, not in parallel) is exceeded, as this happens only, when the server was running 2+ days of processing. To the user it seems, that the application hangs - doing nothing. I used onstat -u to verify that the user is not currently connected to to database. It seems to me, as if the poll-thread or the listener-thread have some problems (maybe the sqlexec cannot be started to whatever reason). The only way to solve this problem is to shutdown and re-init the server (which of course is inconvenient in production-systems). BTW, we are using Online 6.00.UE1 on a RS/6000, AIX 3.2.5. Has anyone encountered simelar problems and a solution (or a workaround) or even a explaination for this specific problem? Thanks in advance, Peter