Yesterday I have got an email with the possible solution:
"In case another of your customers has the same problem, please advise them to add the following registry entry.
Open regedit. Navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Synaptics\SynTPEnh and create a new DWORD called UseScrollCursor with a value of 0.
Restart Windows!
The original fix was published at http://blog.alexou.net/scrolling-in-gtk ... ics-driver.