[Can't change bar color via right click]

This is only a problem on one specific system that is a Mac using Win 7 under parallels. It used to work on his system but now doesn't. 

This is the problem :-

• My program creates a bar chart and displays it
• user clicks on a vertical bar, does a right click, then left click on "color" option
• He is presented with a small bar without any colors to select
• same problem when he tries this via Line Color at the menu bar

This problem does not occur on other PC's and Mac's (I'm talking about several hundred). I've asked him to do a software reload (of my application)

Though it might be a window setting or maybe he has altered a template. 

Any ideas?