Trouble with launching external viewer

[Martin R]

On a completely clean install (ubuntu, sage 9.2.beta11), doing

sage: plot(sin(x), (x,0,3))
Launched png viewer for Graphics object consisting of 1 graphics primitive

or

sage: view(graphs.PetersenGraph())

does not actually launch the external viewer.

doing xdg-open in the sage -sh does.

viewer is 'sage-native-execute xdg-open'

I tried trace, but no error is raised anywhere.  Ideas?

[Martin R]

I just discovered that this only happens when I use xdg-open from within emacs, no matter whether I use ansi-term or something else.