I'm obviously doing something wrong. I drag a connector from core in to breadboard and in inspector change row from single to double and pins to 8 expecting to get a 4 and 4 double row connector. In breadboard it remains an 8 row single connector, as it does in schematic (which may be normal) and in pcb it changes to a two row connector as expected. However if I then select the part in pcb and try and edit it with parts editor I get an error message about unable to read a temp file for Generic double female header - 8 pins generic_double_row_8_100mil not found (and it is entirely correct, there is no such file in the temp directory listed). So what am I doing wrong? I'd say this machine is corrupted except I cleared temp and deleted and reinstalled Fritzing (because I had been muddling around in core parts and may have damaged something) but the clean install does the same thing as do two other installations on Win7 and Win10 on a different machine that I hadn't screwed with the Fritzing core directories on.
Peter