Using 3.4.3 downloaded from LO site. OpenSUSE 11.4 64 bit, custom kernel 3.1, Gnome 2
1. Open new spreadsheet
2. enter sample data in cell A1, A2, select A1
3. Insert->Names->Define enter name eg "One", click 'Add' and 'OK' to close dialog. OK so far.
4. Reopen name dialog, select name "One". 'Assigned to' control is activated.
5. Click in 'Assigned to' control and edit to show name 'One' assigned to A2, click 'Modify'
6. Calc immediately freezes or crashes. Dialog controls are unresponsive. Repeatedly clicking the X to close the dialog finally succeeds in crashing LO Calc, restarting LO allows recovery to continue to last saved point.
Workaround: delete name first, save SS, then create it anew.
I've the same bug on MacOS
*** This bug has been marked as a duplicate of bug 40571 ***