Can't connect to server instances after re-boot

I've set up an informix 11.5 installation on Windows 7 x64 and I'm finding that sometimes after a system re-boot I can no longer connect to server instances. (When trying to connect via dbaccess it will just report "Running . . ." and then return a 908 connection error, and I cannot connect with Server Studio either). Is it possible to re-initialise the instances somehow? Is this likely to be a Windows 7 issue? Where are the host connection details stored under Windows? (as there is no SQL Hosts file are they in the system registry?) Many thanks

Found that the Windows service for each instance was created to start manualy rather than automatically.