Cannot read serial from /sys/bus/usb/devices/

After an update to qemu 1.6 I can't start any of my images. Qemu always crashs. I tried it with root and as a normal user... Here are some log entries I get:

Type: Warning Num: 85
Date: 2013.10.09 23:48:46 549
Sender: bool System_Info::Scan_USB_Sys( QList<VM_USB> &list )
Message: Cannot read serial from /sys/bus/usb/devices/

Type: Debug Num: 86
Date: 2013.10.09 23:48:46 553
Sender: void Virtual_Machine::QEMU_Started()
Message: QEMU Start

Type: Debug Num: 87
Date: 2013.10.09 23:48:46 554
Sender: bool Virtual_Machine::operator==( const Virtual_Machine &vm ) const
Message: Begin

Type: Debug Num: 88
Date: 2013.10.09 23:48:46 554
Sender: bool Virtual_Machine::operator==( const Virtual_Machine &vm ) const
Message: End

Type: Debug Num: 89
Date: 2013.10.09 23:48:46 575
Sender: void Virtual_Machine::QEMU_Started()
Message: emit Loading_Complete()

Type: Debug Num: 90
Date: 2013.10.09 23:48:47 470
Sender: void Virtual_Machine::QEMU_Finished( int exitCode, QProcess::ExitStatus exitStatus )
Message: QEMU Finished

Type: Debug Num: 91
Date: 2013.10.09 23:48:47 470
Sender: bool Virtual_Machine::operator==( const Virtual_Machine &vm ) const
Message: Begin

Type: Debug Num: 92
Date: 2013.10.09 23:48:47 470
Sender: bool Virtual_Machine::operator==( const Virtual_Machine &vm ) const
Message: End

Type: Error Num: 93
Date: 2013.10.09 23:48:47 498
Sender: QEMU Crashed!
Message: