(moved from mailing list)
When I try to see the HU units of a CT-scan in Slicer, I don’t anything in the dataprobe, it doesn’t respond.
But When I look at the nightly versions, the dataprobe works perfectly.
Latest version of Slicer contain many fixes and improvements and it works reliably in general, so probably you’d better use that.
If you must use an older version then you may try to change the viewer layout. As I remember, we’ve fixed a bug some time ago that the Data Probe widget does not work if the layout contains a chart widget on startup. If you switch to another layout (for example, Four-Up layout) and then restart Slicer then it may solve the problem.