Whenever I tried to export a session from Ardour 2.8.4 (build from svn on Ubuntu 9.10) it would hang within a few seconds of starting. I spoke to someone briefly on IRC (thank you for your help!) who pointed out that it was likely to be a Jack problem. At the time I was running the latest jackdmp from Subversion, which was probably risky in hindsight, but downgrading to 1.9.4 seemed to give the same result. In the end I went right back to using 0.116? from the Ubuntu repository and export worked just fine.
I guess what I am asking is, a) could this be caused by some other issue or part of my system that is clashing with the latest Jack or b) should I be reporting this somewhere as a bug with the Jack developer(s).
Stuart