Cannot export in ardour 3.5

I just installed Ardour 3.5 a few hours ago in Ubuntu studio 12.04. I recorded a track, exported it and it went fine.
Then I had to figure out how to mount an sd card (which is another issue in ubuntu) so that I could export directly to it. Apparently, after I did this, ardour can’t export anymore. It just stays stuck on “exporting timespan 1 of 1”. A file is created in the folder (on the harddisk) but it doesn’t get bigger than a few bytes.

What could be the problem here?

I can 't export at all.

I use jack with an alsa driver in the settings of qjackctl. Do you mean that I have to switch to another audio driver?

These problems are generally believed to be caused by the version of JACK that you have installed on your system OR (in a few cases) by the presence of plugins that use multiple threads and are not compatible with faster-than-realtime processing. There are not very many such plugins, so I would guess that it is probably the version of JACK.

alsa jack bridge has caused problems in the past in kx studio but that seems to be fixed now. if you have the alsa bridge running try stopping it.

I didn’t install extra plugins, so I would exclude that possibility.
What do you mean by the version of jack? The difference between jackd, jackd1 or jackd2?

It appears that when I try to export a certain range. The playhead goes up to the first range-marker and then everything stops.

Alexis73: the problem is known to affect most versions of Jack2 until very recently. The problem may still, in fact, be present in Jack2.