In the last couple of days, CSI has informed our RST Product Team that when trying to send a RST2008 .rvt model to ETABS 9.1.5 several of their customers have encountered an error message saying: "Attempted to read or write protected memory. This is often the indication that other memory is corrupt" .
Me too, I am able to reproduce this issue on my machine and I have already reported this problem to our Revit Development team. Several of our developers are currently investigating and working on this issue.
Once I get any comments from our development, I will let everyone know, so stay tune.
Revit Structure Product Manager