Firefox/Thunderbird won't download files/attachments

[Chris A]

When I try to download/save files/attachments from Firefox/Thunderbird, I get a 0 byte file in my Downloads directory. In Firefox the download is listed as failed; in Thunderbird I'm not sure there's a way to get this information.

In both cases if I "Open with..." instead of download then it works. In this case the files are saved to /tmp/mozilla_chris0 and I can access them from there. Permissions on /tmp/ are root:777 and on /tmp/mozilla_chris0 are chris:700. I have tried various permissions setup on my Downloads directory but no difference.

This is on a fresh Disco minimal install (was on 18.04 until Friday with no such issue). Firefox pre-installed, Thunderbird installed from default repositories.

Firefox 66.0.3
Thunderbird 60.6.1

ProblemType: Bug
DistroRelease: Ubuntu 19.04
Package: firefox 66.0.3+build1-0ubuntu1
ProcVersionSignature: Ubuntu 5.0.0-13.14-generic 5.0.6
Uname: Linux 5.0.0-13-generic x86_64
AddonCompatCheckDisabled: False
ApportVersion: 2.20.10-0ubuntu27
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: chris 26112 F.... pulseaudio
BuildID: 20190410124846
Channel: Unavailable
CurrentDesktop: ubuntu:GNOME
Date: Tue May 7 10:37:39 2019
Extensions: extensions.sqlite corrupt or missing
ForcedLayersAccel: False
IfupdownConfig:
 # interfaces(5) file used by ifup(8) and ifdown(8)
 auto lo
 iface lo inet loopback
IncompatibleExtensions: Unavailable (corrupt or non-existant compatibility.ini or extensions.sqlite)
InstallationDate: Installed on 2019-05-04 (2 days ago)
InstallationMedia: Ubuntu 19.04 "Disco Dingo" - Release amd64 (20190416)
IpRoute:
 default via 192.168.16.1 dev wlp58s0 proto dhcp metric 600
 169.254.0.0/16 dev wlp58s0 scope link metric 1000
 192.168.16.0/22 dev wlp58s0 proto kernel scope link src 192.168.18.170 metric 600
Locales: extensions.sqlite corrupt or missing
PrefSources: prefs.js
Profiles: Profile0 (Default) - LastVersion=66.0.3/20190410124846 (In use)
RunningIncompatibleAddons: False
SourcePackage: firefox
Themes: extensions.sqlite corrupt or missing
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 09/27/2018
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 2.10.0
dmi.board.name: 05JK94
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 9
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvr2.10.0:bd09/27/2018:svnDellInc.:pnXPS139360:pvr:rvnDellInc.:rn05JK94:rvrA00:cvnDellInc.:ct9:cvr:
dmi.product.family: XPS
dmi.product.name: XPS 13 9360
dmi.product.sku: 075B
dmi.sys.vendor: Dell Inc.

[Chris A (c-arderne)]

If the file is open in the browser (eg html, pdf, txt) then I can save that directly with no problem. (e.g. click one of the .txt files above and then hit Ctrl-S.)

But if I right click "Save link as..." on the same file then it fails. Same if it's a file that the browser can't display natively.