WMS  I see similar behavior on my G5 and Intel iMacs, both running Leopard. Window Cleaner opens as expected and seems to do its job for some time, but eventually vanishes from the menu bar. I haven't yet tracked down what kills the application.  
(Version 1.8)

WMS  The program does just what the name suggests, make quick 2-D plots, either sketched by hand or plotted from data. For this use, it seems far better than Numbers, which has a strong urge to plot in 3-D no matter how simple the data set. I had hoped Graph Sketcher would also import and plot columns of data from Excel, but no. I highlighted and copied two columns of numbers in Excel, representing x and y coordinates of data points, only to find that Graph Sketcher places the Excel row numbers in the x-column, while displaying my x values as data labels. A little more work is needed on this feature.  
(Version 1.4.8)