Aptitude, upgrade and pinning

I'd like to upgrade some packages from testing to unstable
My configuration is the following one:

==========================================
samiel@debian:~$ cat /etc/apt/sources.list
# Lenny [Testing]
deb http://ftp.it.debian.org/debian/ testing main contrib non-free
deb-src http://ftp.it.debian.org/debian/ testing main contrib non-free
deb http://security.debian.org/ testing/updates main contrib
deb-src http://security.debian.org/ testing/updates main contrib

# Sid [Unstable]
deb http://ftp.it.debian.org/debian/ unstable main contrib non-free
deb-src http://ftp.it.debian.org/debian/ unstable main contrib non-free

# Marillat for Unstable
deb http://www.debian-multimedia.org sid main
# Marillat for Experimental
deb http://www.debian-multimedia.org experimental main

# Rarewares for Unstable
deb http://www.rarewares.org/debian/packages/unstable/ ./
# Rarewares for Experimental
deb http://www.rarewares.org/debian/packages/experimental/ ./

# Cinelerra
deb http://www.kiberpipa.org/~minmax/cinelerra/builds/sid/ ./
==========================================

==========================================
samiel@debian:~$ cat /etc/apt/apt.conf
APT::Default-Release "lenny";
APT::Cache-Limit 15000000;
Apt::Get::Purge;
APT::Clean-Installed;
APT::Get::Fix-Broken;
APT::Get::Fix-Missing;
APT::Get::Show-Upgraded "true";
APT::Force-LoopBreak=true;
APT::Get::AllowUnauthenticated 1;
==========================================

==========================================
samiel@debian:~$ cat /etc/apt/preferences
Package: *
Pin: release a=testing
Pin-Priority: 990

Package: *
Pin: release a=unstable
Pin-Priority: 900

Package: *
Pin: release o=Unofficial Multimedia Packages
Pin-Priority: 850

Package: *
Pin: release o=xmixahlx
Pin-Priority: 800

Package: *
Pin: release a=experimental
Pin-Priority: 750
==========================================

But aptitude install -f kde/unstable gives me this output:

==========================================
debian:~# aptitude install -f kde/unstable
.
.
.
The following packages were blocked:
k3b libk3b3
0 packages upgraded, 0 installed, 0 to remove and 2 not upgraded.
==========================================

But in testing (and in my system) there is K3b 3.5.5,
while in unstable there is K3b 3.5.6. Is it impossible
to solve the dependencies to upgrade this package?

Thanx!
M.

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