Based on your experience, do you know any reason why IRIS would enter a deadlock/hang state ?
When such thing occurs, it's no more possible to connect to Portal or Studio, despite IRIS service (IRIS.EXE processes) being still active. CPU/memory/network usage are usually very low (eg: it does not occurs because server is overloaded). The only fix is a full restart of IRIS (eg: by clicking on IRIS icon in notification toolbar and choosing appropriate action).