Fix tested and confirmed with Inkscape 0.48+devel r9914 + inkscape-680520.diff on OS X 10.5.8:
Shift+click on the Rx knot now resets both radii for the rounded corners to 0 (instead of crashing), as does Shift+click on the Ry knot.
Ctrl+click on the Rx knot sets Ry to the same value (instead of crashing), as does Ctrl+click on the Ry knot set Rx to the same value (creating symmetrically rounded corners).
No regressions found so far with regard to (not) updating the Rx knot.
Fix tested and confirmed with Inkscape 0.48+devel r9914 + inkscape- 680520. diff on OS X 10.5.8:
Shift+click on the Rx knot now resets both radii for the rounded corners to 0 (instead of crashing), as does Shift+click on the Ry knot.
Ctrl+click on the Rx knot sets Ry to the same value (instead of crashing), as does Ctrl+click on the Ry knot set Rx to the same value (creating symmetrically rounded corners).
No regressions found so far with regard to (not) updating the Rx knot.