Matlab: Some Issues with HeatMap

Please find below a copy of the HeatMap that I generated with Matlab. I have two problems that I would like to address:

1) As you can see, the HeatMap has just three different values that it displays.

Red   = 500
Green = 0
Black = 250

Unfortuantely, the Colorbar displays around 10 different values, even for colors that are not used in the HeatMap. I see no option how I could change that. Does anyone know how I could customise this Colorbar/label so that it just covers the three values actually used?

2) When I try to plot this HeatMap I get the following error message:

hmo = HeatMap(data)
HeatMap object with 20 rows and 20 columns.
plot(hmo);
Error using ==> figure
Invalid property found.
Object Name :  figure
Property Name :  'PagePosition'.
Error in ==> HeatMap.plot at 42
hFig = figure('Renderer',     'ZBuffer',...

I am using Matlab R2011a if this is helpful!

Many thanks for your help! Patrick