Is there anything suspicious in .ganttproject.log file in your home directory?

The .ganttproject.log file was not generated (not sure why) but there was 
indeed some 
suspicious exceptions thrown in the console window as soon as I hovered the 
mouse 
over the Dashboard icon. I've attached a log of the console output from launch 
to 
shutdown.

Ah, yes, I forgot that it is stable GP who generates .ganttproject.log...

Thanks for the stack traces. What happens if you change appearance in 
GanttProject 
settings to, say, Windows?

Windows was the default for me. Changing the appearance to "Plastic" made the 
dashboards appear for me (which, given that the exception occurred in 
com.jgoodies.looks.plastic.PlasticComboBoxUI, seems logical). All other themes 
threw 
errors and caused the dashboards to disappear again.

Are dashboards enabled only for "Plastic" for now?

I thought that I understood the problem, but now I'm not sure :) 
Do you say that those stack traces which you attached appear when appearance is
"Windows" ?

Dashboards are not "enabled" or "disabled" for anything. Apparently there are 
just
problems with some look'n'feels

By "enabled" I guess I mean "functional" :)

The error, with associated stack traces, appear when I use any theme *other 
than* 
Plastic.

OK, thanks for your help! I've managed to reproduce it on Linux and ensured 
that code
from Plastic UI is called when other appearance is selected, which is very 
strange.
Now it qualifies as a bug.