I'm on Impressions 3
Things have moved on a bit here. I now think it is was graphics card driver problem which was causing the crash, and that the dynamic blocks were merely triggering it, rather than being the root cause.
I've had our IT people update the driver, and the problem has been resolved.
I'm still interested in advice on efficient methods for preparing autocad files for export to Impressions, as it seems to me I'm going to have to spend considerable amounts of time tweaking other peoples dwg's to knock them into shape for Impressions.
I realise that in an ideal world they would take the time to prepare their files in the form that I would like, but as they are techies, and I am the only one interested in the arty output of their files, it will be down to me to sort it out.
Thanks for the help.