Problem: Buffer Underflow using multiple switches

[Oliviander]

Hello all,
for some time now I am having a problem
with my streaming setup and don't find
any clues what kind of problem it actually is.

I would like to have (and tried) the following installation

MinS is running on a VMware virutal Win XP System that is running
on a ESXI 5 Hypervisor

Therefore the System is connected to a VM Virtual Switch

This Virtual Switch is Connected to a Main Switch in the Serverroom
(this is a Layer 2 managed Switch )
My Music NAS (not running MinS itself) is connected to the main Switch too

The Main Switch is connected via a tagged Connection to a managed
Floor Switch.

My PC with Kinsky desktop and my Linn Majik DSM
are connected to the floor switch.

Using this setup leads to frequent dropouts
obviously resulting from buffer underruns.

To test this out installed MinS on a
rather powerful physical System too
connected to the main switch.
This setup leads to fewer but still existing dropouts.

Fo another test I installed Asset upnp on the same virtual server
as MinS. This setup had also some but fewer dropouts.
About the same as MinS on the physical server.

As a last test I installed MinS on a rather less powerful Atom PC
but I connected this Computer directly to the floor switch,
and voila no more dropouts.

(I never changed the Connection of the NAS or the Controlpoint
or the renderer in these different setups)

If this Streaming by MInS would be a Broadcast or a Multicast thing
I could imagine how the multiple switches could lead to
a problem.

But in this case ?

Does anybody have an idea ?