Can I use a Dupont cable with a resistor soldered in the middle as a pullup resistor for I2C comms?
No, in normal cases that should make no noticable difference. 

But maybe


the dupont headers don't make good contact with your breadboard
your setup is marginal in some way (frequency too high?) and this extra wiring tripped it over the edge
you made some other mistake (from the 2nd photo it seems that you might have a breadboard that has a halfway break in the power lines, but the last foto is a 400 holes bb which I have never seen with breaks)