Scroll Error

I have a user with an HP t5325 Thin Client who is logging onto a server running Windows 2008 R2 and Office 2007. When she opens a spreadsheet and clicks with the mouse on the scroll bar pointers, (Up and Across) the spreadsheet moves very slowly to the next cell but when pressing a second time it starts scrolling slowly and then shoots across to either half way across or down. I have deleted the users profile and tried logging in again but the problem remains. If I use the Thin Client I do not have the same problem.
Has anyone else had this problem and if so how did you fix it?

I have managed to reproduce the error with another user and changing the double click rate of the mouse fixed his issue but not the original.