Can't get a USB <-> Serial converter based on Moschip 7840 to work

I've just upgraded my server from Gutsy to Hardy.
Most of my applications is still working (eventhough some fixes where needed). However there is one final thing that doesn't work; my USB <-> Serial converter.

The converter is identified by the system that the mos7840 module is loaded. But when the module should identify the converter I get the message "probe of 8-1:1.0 failed with error -5". When running Gutsy everything worked fine.

See below for log extracts from dmesg from my server running Gutsy and Hardy. I've also included an verbose listing of lsusb on the converter.

Output from dmesg in Hardy:
[ 38.565449] /build/buildd/linux-2.6.24/drivers/usb/serial/mos7840.c: Moschip 7840/7820 USB Serial Driver 1.3.1
[ 38.565472] mos7840: probe of 8-1:1.0 failed with error -5
[ 38.565480] usbcore: registered new interface driver mos7840

Output from dmesg in Gutsy:
[ 34.265121] /build/buildd/linux-source-2.6.22-2.6.22/drivers/usb/serial/mos7840.c: Moschip 7840/7820 USB Serial Driver 1.3.1
[ 34.265140] mos7840 8-1:1.0: Moschip 7840/7820 USB Serial Driver converter detected
[ 34.271350] usbcore: registered new interface driver mos7840

lsusb -v
Code:

Bus 008 Device 003: ID 9710:7840 MosChip Semiconductor
Device Descriptor:
  bLength 18
  bDescriptorType 1
  bcdUSB 2.00
  bDeviceClass 255 Vendor Specific Class
  bDeviceSubClass 0
  bDeviceProtocol 255
  bMaxPacketSize0 64
  idVendor 0x9710 MosChip Semiconductor
  idProduct 0x7840
  bcdDevice 0.01
  iManufacturer 0
  iProduct 0
  iSerial 0
  bNumConfigurations 1
  Configuration Descriptor:
    bLength 9
    bDescriptorType 2
    wTotalLength 81
    bNumInterfaces 1
    bConfigurationValue 1
    iConfiguration 0
    bmAttributes 0xa0
      (Bus Powered)
      Remote Wakeup
    MaxPower 100mA
    Interface Descriptor:
      bLength 9
      bDescriptorType 4
      bInterfaceNumber 0
      bAlternateSetting 0
      bNumEndpoints 9
      bInterfaceClass 255 Vendor Specific Class
      bInterfaceSubClass 0
      bInterfaceProtocol 255
      iInterface 0
      Endpoint Descriptor:
        bLength 7
        bDescriptorType 5
        bEndpointAddress 0x81 EP 1 IN
        bmAttributes 2
          Transfer Type Bulk
          Synch Type None
          Usage Type Data
        wMaxPacketSize 0x0200 1x 512 bytes
        bInterval 255
      Endpoint Descriptor:
        bLength 7
        bDescriptorType 5
        bEndpointAddress 0x02 EP 2 OUT
        bmAttributes 2
          Transfer Type Bulk
          Synch Type None
          Usage Type Data
        wMaxPacketSize 0x0200 1x 512 bytes
        bInterval 255
      Endpoint Descriptor:
        bLength 7
        bDescriptorType 5
        bEndpointAddress 0x83 EP 3 IN
        bmAttributes 2
          Transfer Type Bulk
          Synch Type None
          Usage Type Data
        wMaxPacketSize 0x0200 1x 512 bytes
        bInterval 255
      Endpoint Descriptor:
        bLength 7
        bDescriptorType 5
        bEndpointAddress 0x04 EP 4 OUT
        bmAttributes 2
          Transfer Type Bulk
          Synch Type None
          Usage Type Data
        wMaxPacketSize 0x0200 1x 512 bytes
        bInterval 255
      Endpoint Descriptor:
        bLength 7
        bDescriptorType 5
        bEndpointAddress 0x85 EP 5 IN
        bmAttributes 2
          Transfer Type Bulk
          Synch Type None
          Usage Type Data
        wMaxPacketSize 0x0200 1x 512 bytes
        bInterval 255
      Endpoint Descriptor:
        bLength 7
        bDescriptorType 5
        bEndpointAddress 0x06 EP 6 OUT
        bmAttributes 2
          Transfer Type Bulk
          Synch Type None
          Usage Type Data
        wMaxPacketSize 0x0200 1x 512 bytes
        bInterval 255
      Endpoint Descriptor:
        bLength 7
        bDescriptorType 5
        bEndpointAddress 0x87 EP 7 IN
        bmAttributes 2
          Transfer Type Bulk
          Synch Type None
          Usage Type Data
        wMaxPacketSize 0x0200 1x 512 bytes
        bInterval 255
      Endpoint Descriptor:
        bLength 7
        bDescriptorType 5
        bEndpointAddress 0x08 EP 8 OUT
        bmAttributes 2
          Transfer Type Bulk
          Synch Type None
          Usage Type Data
        wMaxPacketSize 0x0200 1x 512 bytes
        bInterval 255
      Endpoint Descriptor:
        bLength 7
        bDescriptorType 5
        bEndpointAddress 0x89 EP 9 IN
        bmAttributes 3
          Transfer Type Interrupt
          Synch Type None
          Usage Type Data
        wMaxPacketSize 0x0010 1x 16 bytes
        bInterval 5
Device Qualifier (for other device speed):
  bLength 10
  bDescriptorType 6
  bcdUSB 2.00
  bDeviceClass 255 Vendor Specific Class
  bDeviceSubClass 0
  bDeviceProtocol 255
  bMaxPacketSize0 64
  bNumConfigurations 1
Device Status: 0x0000
  (Bus Powered)

I've run out on ideas on how to handle the error. Any ideas?

/Andreas