Help system (for Demo files) does not display content ?

Hi, I'm not sure when this problem happened, or its potential cause(s).

If I type the 'demo' command and press enter, a hierarchical Table of Contents shows, which I can navigate and then when I choose the item of interest, I get the MATLAB logo and only "Loading...."

I have a student version 2011a, recently updated with another toolbox. Otherwise MATLAB is working and the license files are/were intact.

EDU>> ver
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MATLAB Version 7.12.0.635 (R2011a)
MATLAB License Number: STUDENT
Operating System: Microsoft Windows XP Version 5.1 (Build 2600: Service Pack 3)
Java VM Version: Java 1.6.0_17-b04 with Sun Microsystems Inc. Java HotSpot(TM) Client VM mixed mode
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MATLAB                                                Version 7.12       (R2011a)
Simulink                                              Version 7.7        (R2011a)
Aerospace Blockset                                    Version 3.7        (R2011a)
Aerospace Toolbox                                     Version 2.7        (R2011a)
Communications System Toolbox                         Version 5.0        (R2011a)
Control System Toolbox                                Version 9.1        (R2011a)
DSP System Toolbox                                    Version 8.0        (R2011a)
Data Acquisition Toolbox                              Version 2.18       (R2011a)
Fixed-Point Toolbox                                   Version 3.3        (R2011a)
Fuzzy Logic Toolbox                                   Version 2.2.13     (R2011a)
Image Processing Toolbox                              Version 7.2        (R2011a)
Instrument Control Toolbox                            Version 2.12       (R2011a)
Optimization Toolbox                                  Version 6.0        (R2011a)
Signal Processing Toolbox                             Version 6.15       (R2011a)
SimElectronics                                        Version 1.6        (R2011a)
SimMechanics                                          Version 3.2.2      (R2011a)
SimPowerSystems                                       Version 5.4        (R2011a)
Simscape                                              Version 3.5        (R2011a)
Statistics Toolbox                                    Version 7.5        (R2011a)
Symbolic Math Toolbox                                 Version 5.6        (R2011a)
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