Hi Anton,
indeed there was a bug.  Following patch applied to
gazebo/gazebo-svn/server/physics/ode/ODEHingeJoint.cc should fix the issue.
I'll ticket this and make a release patch.

Index: server/physics/ode/ODEHingeJoint.cc
===================================================================
--- server/physics/ode/ODEHingeJoint.cc    (revision 8600)
+++ server/physics/ode/ODEHingeJoint.cc    (working copy)
@@ -129,7 +129,7 @@
 /// Set the velocity of an axis(index).
 void ODEHingeJoint::SetVelocity(int /*index*/, double angle)
 {
-  this->SetParam(angle, dParamVel);
+  this->SetParam(dParamVel,angle);
 }

 //////////////////////////////////////////////////////////////////////////////

Thanks!
John

On Tue, Mar 30, 2010 at 9:26 PM, Antons Rebguns <arebgun@gmail.com> wrote:

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> Hash: SHA1
>
> Folks,
>
> I am running from the "latest" tag with Gazebo simulator at rev 28511 (i.e.
> it's an unstable version 1.1.1). I have a
> pretty weird problem when adding my robot to the environment - the robot
> jumps around for a few seconds until settles
> down. It used to work fine in stable version of gazebo.
>
> The problem seems to be in gazebo_ros_diffdrive plugin. If I comment out
> line 95:
>
> this->posIface->data->cmdEnableMotors = 1;
>
> then it does not jump around and starts up normally, but then of course I
> can't control it. Here is the link to the
> video of what's happening exactly:
>
> http://one.ubuntu.com/p/Md/
>
> Any ideas on what might be happening?
>
> Thanks,
> Anton
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