PICDEM FS USB CDC demo under Linux

I am trying to get the CDC demo working under Linux.

It is recognized as ttyACM0 (CDC_ACM device). However communication
program seems not really successful using minicom/cutecom/gtkterm.

It seems that I can only writing to the virtual com port but not
read from the com port. Hot plugging also cause timeout problem.
I am working with the default Microchip CDC firmware and under 
Windows, hypertiminal or other application works without a problem. 
Python with pyserial also works under Windows.

Has anybody made it work already? Any suggestion to make it work?
I've tried a simple libusb program but set_configuration failed.

Regards,
Xiaofan

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This is part of the output from dmesg: 
usb 2-4: USB disconnect, address 5 
ohci_hcd 0000:00:02.1: wakeup 
usb 2-4: new full speed USB device using ohci_hcd and address 6 
drivers/usb/class/cdc-acm.c: This device cannot do calls on its own. It is
no modem. 
cdc_acm 2-4:1.0: ttyACM0: USB ACM device 

-----------------------------------------------------
This is the detail decription from lsusb -v. 
Bus 002 Device 013: ID 04d8:000a Microchip Technology, Inc. 
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass            2 Communications
  bDeviceSubClass         0 
  bDeviceProtocol         0 
  bMaxPacketSize0         8
  idVendor           0x04d8 Microchip Technology, Inc.
  idProduct          0x000a 
  bcdDevice            0.00
  iManufacturer           1 
  iProduct                2 
  iSerial                 0 
  bNumConfigurations      1
  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength           67
    bNumInterfaces          2
    bConfigurationValue     1
    iConfiguration          0 
    bmAttributes         0x80
    MaxPower              100mA
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       0
      bNumEndpoints           1
      bInterfaceClass         2 Communications
      bInterfaceSubClass      2 Abstract (modem)
      bInterfaceProtocol      1 AT-commands (v.25ter)
      iInterface              0 
      CDC Header:
        bcdCDC               1.10
      CDC ACM:
        bmCapabilities       0x02
          line coding and serial state
      CDC Union:
        bMasterInterface        0
        bSlaveInterface         1 
      CDC Call Management:
        bmCapabilities       0x00
        bDataInterface          1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x82  EP 2 IN
        bmAttributes            3
          Transfer Type            Interrupt
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0008  1x 8 bytes
        bInterval               2
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        1
      bAlternateSetting       0
      bNumEndpoints           2
      bInterfaceClass        10 Data
      bInterfaceSubClass      0 Unused
      bInterfaceProtocol      0 
      iInterface              0 
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x03  EP 3 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x83  EP 3 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0