While interactively changing a design and launching either the RTL or Technology Viewer, the viewer crashes if the previous instances of the viewer are not closed.
The very first design change always works and opens a schematic in a second window. Attempting to open a third schematic RTL/Technology view causes the viewer to crash.
To work around this issue, close each RTL/Tech view before opening the next.
This issue has been resolved in the ISE Design Suite 11.3 update.