[PROBLEM] Tv-Stream from Mediaportal freezes peridiodically for ~18s

[Dracul]

Software
XBian version: 1.0Beta2
XBMC version:XBMC Git:12.2 Git:20131125-d1002b4
Overclock settings: Xbian default and turbo(to test)
RPI Firmware: Linux xbian 3.10.18+ #68 Sat Nov 16 00:50:06 CET 2013 armv6l GNU/Linux
GPU Firmware: Oct 1 2013 00:37:09 Copyright © 2012 Broadcom
version a421d4b2cee544ec22bd4eee75080248f18fc20b (tainted) (release)

I've tested raspbmc to with the same problem. I've changed the Server OS and Hardware to from Windows Server 2012 to Windows 8.

Hardware
Power supply rating: 5V 1A and i tested 5V 2,5A too
RPi model (model A/B 256mb/512mb): B 512
SD card size and make/type:i've tested: Transcend 8GB Class 10, Kingston 2GB Class ?, Kingston 2GB Class ? only as boot + USB Stick
Network (wireless or LAN): tested on wireless and wired lan
Connected devices (TV, USB, network storage, etc.): TV

Logile
http://ul.to/c9o5apyb
*.rar and *.log dont work as attachment


Problem description:
After a fresh install i updated the system wie sudo apt-get update/upgrade. I set the resolution to 1280*720p and the gui to 720p. Then i install the pvr plugin for Mediaportal and configure it.

I can watch SD TV and SD Recordings, but HD TV and HD Recordings freezes every ~30s for ~18s. Normal mkv over network(smb) works fine, so do HD Recordings over nfs.

I changed the cache in the advancedsettings.xml to(<pvr>). I've changed the Server OS and Hardware to from Windows Server 2012 to Windows 8.Whatever i have tried, there was no improvement.

But HD TV should work according to other users.

How to reproduce:
Every time i start HD TV or HD Recording over Mediaportal pvr plugin.