Just got hit by this problem, whenever I tried to deploy my application:
11:06:04: Package created.
11:06:04: Installing package to sysroot ...
Package 'untitled' installed.
11:06:04: Preparing SFTP connection...
11:06:04: Starting upload...
11:06:04: Failed to upload package: Failure
11:06:04: Deploy step failed.
Error while building project untitled (target: Harmattan)
When executing build step 'Deploy Debian package via SFTP upload'
And a notification warning about the little remaining data storage appeared on the device, which I wrongly ignored at first. The problem occurs because QtCreator tries to copy the debian packate to /tmp on the device, N9 for me, and it fails if the space is full. I managed to fill my /tmp partition (which is just 4Mb btw..) by testing some big application. Solution is, ssh to your device, check if you /tmp is full (df -h) and delete any .deb file left there by QtCreator.
/home/developer $ df -h
Filesystem Size Used Available Use% Mounted on
/dev/root 3.9G 1.7G 2.0G 47% /
devtmpfs 10.0M 248.0K 9.8M 2% /dev
tmpfs 4.0M 4.0M 0 100% /tmp
tmpfs 512.0K 148.0K 364.0K 29% /var/run
..
/dev/mmcblk0p3 2.0G 197.7M 1.7G 10% /home
/tmp $ cd /tmp && ls -al
total 4096
..
-rw-r--r-- 1 user develope 0 Feb 7 09:59 qstardict_0.0.3_armel.deb
-rw-r--r-- 1 user develope 0 Feb 7 10:06 qstardict_0.0.4_armel.deb
-rw-r--r-- 1 user develope 4116480 Feb 3 21:32 qxmpp_0.0.1_armel.deb
..
/tmp $ rm qstardict_0.0.3_armel.deb
/tmp $ rm qxmpp_0.0.1_armel.deb
/tmp $ rm qstardict_0.0.4_armel.deb
UPDATE: This is supposed to be fixed on QtCreator 2.5 according to https://bugreports.qt-project.org/browse/QTCREATORBUG-6859
Patch is here if you don’t want to wait :) : http://qt.gitorious.org/+qtcn/qt-creator/qtcn-qt-creator/commit/b7d02e08fa246f3d45c898dc2480143a372409f0