While reading larger .pdf-Files I like to lean back and use spacebar instead of PageDown for rolling through the document. It only switches to the hand tool.
I'm using current http://neo-layout.org/neo20.exe (working at a Windows Terminal Server 2003 without admin rights) and Adobe Reader X. If I deactivate or stop neo20.exe all works fine.
In Firefox at the same machine pressing spacebar rolls down like expected.