As many of you are aware the NX4 web client is prone to crashing and corrupting RCE sessions. We recommend against using the web client and instead you should use the desktop client. Instructions for downloading and installing the NX4 desktop client can be found here: http://projects.iq.harvard.edu/rce/nx4_installation
Things to check if you are unable to connect to the RCE:
Is there an active outage? We post any outages to the RCE itself, our RCE calendar, and to our outages mailing list in advance of planned maintenance windows. You can also check the HMDC status page. For more information, please see our page on RCE outages.
Are you over quota? If your home directory goes over 2GB, you won't be able to log in to a RCE desktop. Log in via SSH to clean up your home directory. See, How Do I Check My Quota? for more information.