Yes, it says "Java VM: Java Hotspot(TM) Server VM, Sun Microsystems inc."
I downloaded the recent linux version from the website and installed it.
There are no other errors that happen before or after the freeze.
It seems to me that it happens after a number of operations. I switch between a few different programs when editing diagrams. Sometimes it is possible to use yEd for a long time, sometimes keyboard input freezes after a few minutes. I am not sure, if it has to do with certain operations, because I do similar operations all the time and it only just happens after some time. I create nodes, label them directly after creating, create child nodes and duplicate notes that I rename, restructure the connections between them often and try diffent layout options for best display. I use the keyboard for most operations. The diagramms are small, about 10 to 30 nodes. I have 3-4 open at the same time, but it seems to happen with only one open diagram too. It seems to me that sometimes it happens after creating a node, sometimes after editing a label, sometimes after changing layout and sometimes after switching programs.