I use my touchpad for up/down scrolling so didn't notice this before. So - trying to make my question more accurate. Both scroll bars - up/down & left/right - are missing and I can't find a way to get them back again.

Hi.

There are several more topics on the forum about tablet issues, maybe one has the right solution for you.

Check this topic, maybe it will help:
http://www.inkscapeforum.com/viewtopic.php?f=5&t=15360

If you mean the visible scroll bars at the side and bottom of the window, try View > Show/Hide > Scrollbars. It's also bound to the CTRL-B keyboard shortcut, which seems a little daft to me, as I could easily see someone accidentally turning them on or off when they think they're emboldening some text.