linphone and ekiga crash repeatable on video phone calls on amd64

[Casandro]

Both linphone and ekiga crash repeatable when starting a video phone call. This only happens on 64 bit machines, not on 32 bit machines.

Linphone manages to chuck out this short error message:
[mpeg4 @ 0x7f8c90009c80] rc buffer underflow
Speicherzugriffsfehler

The webcam works fine with guvcview.

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: linphone 3.3.2-4.1
ProcVersionSignature: Ubuntu 3.0.0-16.28-generic 3.0.17
Uname: Linux 3.0.0-16-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 1.23-0ubuntu4
Architecture: amd64
Date: Sun Mar 25 11:56:29 2012
InstallationMedia: Xubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111011)
ProcEnviron:
 PATH=(custom, no user)
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: linphone
UpgradeStatus: No upgrade log present (probably fresh install)