Hi Hans,
I have exactly the same CPU usage (while navigating, drops to around 15% while no navigation) and memory usage (around 1.25 GB) while the model is imported. Except no crashes under Windows 7.
To really push this test hard, I produced this render, on a 1.6GHz Netbook, with 2GB of ram. While also watching full screen YouTube videos.
Still no crashes.
Here is the render.
Is it possible that it could be either the Linux distro or a faulty memory module that might be causing your program instabilities?
One reason why Sweet Home might crash for you, while other programs don't, memory problems don't usually become obvious, until something really taxes their usage.
Did the person who fitted your memory modules, wear an anti static discharge wrist strap?
How is the Visualization going? If it is up and running, please could you try the same test, running the Windows version of Sweet Home, within the Windows 7 virtual machine, if it doesn't crash there, then it isn't your memory. Just trying to help think of ideas to solve your Sweet Home crashes.
db4tech
