Tvheadend

Dear Tvheadend user,

I own a half year a DVBsky 960 (usb) tuner.
4 weeks ago i ordered a second DVBsky 960 (usb) tuner.
so that i can watch tv and record on the same time.
Everything works well for a a day
But after a day the software/hardware breaks down.

The 2 dvbsky tuners(dvb-s2) and 1 terratec h5 (dvb-C) tuner are connect to a pc with
AMD E-350 processor with intergated graphics.
and 4 gb of ram.

The software that i installed on that pc are:

Linux ubuntu server13.04.
ssh server
Tvheadend 2.5.xxx (latest version)
The latest DVBSky drivers pack + firmware.

Everthing wordk well for 1 or two daysIf tvheadend breakdown i see in Dmesg the following errors

[ 4059.760008] usb 2-1: USB disconnect, device number 2
[ 4059.776253] usb 2-1: dvb_usb_v2: usb_bulk_msg() failed=-19
[ 4059.776445] usb 2-1: dvb_usb_v2: usb_bulk_msg() failed=-19
[ 4059.776557] m88ds3103_readreg: reg=0xa2 (error=-19)
[ 4059.776666] usb 2-1: dvb_usb_v2: usb_bulk_msg() failed=-19
[ 4059.776782] m88ds3103_writereg: writereg error(err -19, reg 0xa2, value == 0xec)
[ 4194.644713] INFO: task khubd:25 blocked for more than 120 seconds.
For more Dmesg info the attachment.

Is this a software problem? (Tvheadend, driver pack, Linux)
Or is it hardware related (bios settings, faulty dvb hardware)

Please can you help me to solve this problem?