Cant ping / connect to 3/4 switches

I have 5 switches Dell Powerconnect 5324 on my network - one of them has broken.  I cannot ping 3 out of the 4 remaining switches.  The switches are all connected to switch one only.  Any ideas why i cannot ping the others?

I cannot connect directly to the switch as the IP will not ping and i have no RS-232 crossover cable - is there another way?