Thanks for your reply, Luc. The bug was mentioned in a couple of threads from the middle of last year (they came up when I was searching for a solution before posting), the description of the camera behaviour sounds similar to that I am experiencing.
http://discourse.mcneel.com/t/uncontrolled-camera-rotation/9808
I wondered if the trial version I am using had the service release applied as I don’t seem to be able to check for updates. I have actually contacted my reseller to buy a licence so once that comes through I’ll try an update.
I’ll have to check with my client before sending the file, hopefully won’t be a problem. I’ll get back to you on that.
Thanks for your help.