Wacom Penabled Tablet PCs Stylus not recognized

Inkscape version: ALL, tested up to 0.48.1-2, newer development version not tested.
Operating System: Windows 7 X64 with Service pack 1
Hardware tested: Lenovo Thinkpad X201 Tablet (none-touch screen)

###Problem###
Inkscape does not recognize the built-in-LCD Wacom digitizer on tablet PCs (Wacom Penabled tablet PC). No extended input device can be found, only the core pointer device is displayed on the input device list. One can still draw using the stylus but no pen pressure can be detected.

###Inkscape Configuration###
In Inkscape, Use pressure-sensitive tablet, CHECKED or UNCHECKED.
Switch tool based on tablet device, CHECKED or UNCHECKED.
All no go.

###Driver###
Wacom Multitouch ISD driver 7.0.2.19 is installed. Probably all earlier version are tested, too. None of them seem to help.

Wacom Penabled LCDs are coupled with a special driver called Wacom ISD driver, it has a build-in touch sensitive input function, which is similar to Bamboo Touch. The driver is not compatible with any other Wacom products. The driver package installs a different set of devices: 1) Wacom HID Digitizer, 2) Wacom HID Pen, 3) Wacom Penabled MiniDriver, 3) Wacom Virtual Hid Driver. And it also installs different services: TabletServiceISD, C:\Program Files\Tablet\ISD\ISD_Tablet.exe These are all different from other normal Wacom tablets.

###Related Windows Services###
Enabling or disabling the "Tablet PC Input Service" in Windows service management.
Makes no difference.

###Workaround###
However, if an external tablet device (Bamboo Fun or Intuos 4 tested) is connected with their driver properly installed, Inkscape detects both the built-in-LCD digitizer and the external tablet. Once selected in the input device list, they all work fine with pressure sensitive. In such circumstance, the built-in-LCD digitizer is detected as "Wacom Tablet ISD Stylus" & "Wacom Tablet Eraser". When the external tablet got removed, the built-in-LCD tablet also disappears from the input device list and stops working.

###GIMP###
GIMP, which also use GTK+, has affected by this issue, too. Tested and confirmed on GIMP 2.6.11 and 2.7.3. The problem and workaround are almost the same. Maybe this is a shared issue in all GTK+ programs?

###Other Commercial painting tools###
The CELSYS illuststudio 1.2.1 seems to have a similar issue, too, it detects the built-in-LCD digitizer, but the pressure sensitive is not working. Adobe photoshop CS5, Autodesk Sketchbook Design 2012 are working perfectly on the system without any configuration.