Hmm, strange. For what it's worth afterall, here's what I did when I noticed it (nothing special, really):
- Start DPlot
- <Generate-Y=f(X)> (simple X^2+X function, X-range [-10,10])
- <Options-Reference Lines>
- <Add> (X=0)
- now when either adding other reference lines like Y=0, followed by deleting them again or deleting the very first added one right away: once the last one left is deleted DPlot closes down.
The same when I add and delete in two independent Reference lines dialog sessions: add-OK; going back to reference lines dialog again and delete.
On my pc (Win XP Home, SP2) everything is reproducable.
Hope this additional info helps although I doubt it
Roberto