I'm really sorry about this. We recently discovered a problem with the way that the NGINX webserver was configured on GVL 4.2. We were able to quickly change the configuration, but this new configuration will only apply to new VMs launched after 15th of July.
If you frequently use the web services (RStudio, VNC, Cloudman) on GVL, the simplest remedy is to launch a new GVL using the updated configuration and delete your current one, after you've backed up any data of course.
If you just use the command line via SSH, everything on your instance will still work correctly, apart from the web page. You can continue to use the command line utilities on this instance, or use the command line to transfer any data to a new instance using
rsync, and then delete the old instance.
Apologies again for the inconvenience, and please drop me a line if anything is unclear, or if there's anything we can do to help transfer you to a new instance.