Upload synching fails with "Unknown error" with file > 3MB

I am trying to sync a directory with owncloud-client. Most of the files went fine, but three of them are bigger than 3MB, and all these fail with "Unknown error".

Here is the log:
04-03 11:59:37:819 ** PUT request to /remote.php/webdav/Contrat-pret.pdf
04-03 11:59:37:819 hbf_splitlist block_size: 10485760 threshold: 10485760 st_size: 14494816
04-03 11:59:37:819 hbf_splitlist num_blocks: 2 rmainder: 4009056 blk_size: 10485760
04-03 11:59:37:819 hbf_splitlist created block 0 (start: 0 size: 10485760)
04-03 11:59:37:819 hbf_splitlist created block 1 (start: 10485760 size: 4009056)
04-03 11:59:37:819 About to upload "Contrat-pret.pdf" ( "" 14494816 bytes )
04-03 11:59:37:819 hbf_transfer PUT request to /remote.php/webdav/Contrat-pret.pdf
04-03 11:59:37:819 _hbf_dav_request Block: 0 , Start: 0 and Size: 10485760
04-03 11:59:56:710 !!! Mirall::CheckQuotaJob created for QUrl( "https://webcloud6.zaclys.com" ) querying "/"
04-03 12:00:12:439 void Mirall::CSyncThread::transferCompleted(const Mirall::SyncFileItem&) "Contrat-pret.pdf" 2 "Unknown error."

While the file is syncing, I can see the amount of data sent climbing up to 3MB, and then fail.

I have tried the following:
Syncing the same file on the same owncloud server succeded from a Win XP virtual machine (on the same physical machine) with owncloud sync client v.1.5.3.

Syncing the file from the server to my machine (Ubuntu) went fine also.

Installing the "official" owncloud-client 1.5.3 from opensuse repositories alos fails with "unknown error"

I can make any test that is needed.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: owncloud-client 1.5.0+dfsg-4ubuntu1
ProcVersionSignature: Ubuntu 3.13.0-22.44-generic 3.13.8
Uname: Linux 3.13.0-22-generic x86_64
ApportVersion: 2.14-0ubuntu1
Architecture: amd64
CurrentDesktop: Unity
Date: Thu Apr 3 16:04:42 2014
InstallationDate: Installed on 2013-02-16 (410 days ago)
InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Alpha amd64 (20130216)
SourcePackage: owncloud-client
UpgradeStatus: Upgraded to trusty on 2014-01-22 (70 days ago)