I just started IDEA 7348 (after shutting down 7343) and it complained that it couldn't check whether another instance of IDEA was running or not. However the message in the dialog is a little confusing as it reads: "Please troubleshoot your TCP/IP configuration and/or local firewall settings. and attach the c:\temp\blahblah\idea.log file" It looks like the last sentence was meant for some other error message or something. (Note that at the same time, it's weird that it can't check for multiple instances.. all builds up to 7343 were just fine.)