[Paraview] Error: Could not determine discrete values (if scalar value > 31)

[Michael Nolde]

Hello,

I could use some help with vizualizing an unstructured grid.
I've got an .VTU / XML file with values in a scalar field, which act as 
color ids. I want to colorize my mesh according to these values. The 
values should be interpretet as categories, so I checked this option in 
ParaView. As long as my values are below or equal 31, everything works 
out fine. But as soon as I use the full data range (242 different 
values), ParaView gives an error:  Could not determine discrete values 
using the data produced by the current source/filter. Please add 
annotations manually.
If I do enter some values by hand, it works nicely again. But entering 
more than 200 values by hand is not really an option.
To see if the determination fails because of missing values between 0 
and 242, I checked the scalars, but everything seems to be fine.

Could anyone give me a hint on how to proceed / what to try?

Thanks, cheers,
Michael