I tested Flooring.lwa that is on your linked page and it is fine.
Generally, proprietary surfaces cannot be used in Archicad since there is no way to lock them. Imagine the lawsuit if some duffus edited a paint color at your office and didn't tell.....
As for crashing - that is odd. Are you putting your new .lwa archives in the folder with the ones already in Archicad?
Dwight Atkinson