File-Roller + 7z doesn't split a file into parts greater than 2.1GB

[MaLa]

1) I want to split an ISO image into 2 or 3 parts of 4GB.
2) I can split a file with File-Roller and 7z and I can decide the size of each parts
3) I start the compression and splitting and I see that the size of each parts isn't the same size that I have decide before. It is 2.1GB.
4) If I execute the 7z command on the terminal this problem doesn't exist.

Can someone resolve it?

Thank you so much!

Marco

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: file-roller 3.4.1-0ubuntu1
ProcVersionSignature: Ubuntu 3.2.0-31.50-generic 3.2.28
Uname: Linux 3.2.0-31-generic i686
ApportVersion: 2.0.1-0ubuntu13
Architecture: i386
Date: Thu Sep 27 15:20:13 2012
ExecutablePath: /usr/bin/file-roller
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release i386 (20110427.1)
SourcePackage: file-roller
UpgradeStatus: Upgraded to precise on 2012-06-10 (108 days ago)