encrypt/decrypt on CIFS share does not work with seahorse-tool for files > 57kb

Binary package hint: seahorse-plugins

Encrypting and decyrypting files with seahorse-tool (via right-click in nautilus) fails on cifs shares. It still works on locally mounted disks.

Looks like seahorse-tool has problems working with files on a cifs share, if file size is above 57k.

Symptoms:
- Copying files per cp or drag-and-drop onto and from the cifs share works without errors
- PGP-encrypting a file via right click on a cifs share leads to the generation of a .pgp file. But this file seems to be cut off at a maximum size of 57344 bytes. The original file had 251327 bytes. When I try to decrypt the file, it chooses the right key, but the produced file is unreadable (probably just misses the previously cut-off part).
- When trying to decrypt a healthy .pgp file (can be decrypted on a local disk w/o problems), de-cryption produces a file that is again cut-off at 57344 bytes.
- Encrypting and de-crypting a file of only 28k works fne on the cifs share

The syslog shows the following error message:
  montreal kernel: [ 934.789391] CIFS VFS: Send error in Close = -512
sometimes the log also shows
  montreal kernel: [ 4794.063692] CIFS VFS: Send error in Close = -11
but I cannot say whether it relates to seahorse.

I have been using seahorse on cifs shares for years on ubuntu 10.10 and did not experience this issue.

The samba server is a ubuntu 10.10 KVM domain on a ubuntu 10.10 server:

Linux ubuntu-samba 2.6.35-28-server #50-Ubuntu SMP Fri Mar 18 18:59:25 UTC 2011 x86_64 GNU/Linux
samba 2:3.5.4~dfsg-1ubuntu8.4

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: seahorse-plugins 2.30.1-3ubuntu2
ProcVersionSignature: Ubuntu 2.6.38-8.42-generic 2.6.38.2
Uname: Linux 2.6.38-8-generic x86_64
Architecture: amd64
Date: Tue Jun 21 13:18:20 2011
EcryptfsInUse: Yes
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427.1)
ProcEnviron:
 LANGUAGE=de_DE:en
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: seahorse-plugins
UpgradeStatus: No upgrade log present (probably fresh install)