Camaras doesn't shows signals

i'm sorry for my english

i have 6 cameras, they had been working since 2003 but now the led corresponding to the port in the hub of one of them lights orange (trouble indicator) when all the others leds lights green
i disconnect every camara one by one, (i have read now that i must turn off all of them before to restart the system even the hub)
i haven't
check the voltage on the ac adapter (if one of them is working no more)
Change the utp cable (is the original from the first installation and all the other port turn light green only one doesnt)
unisntall the Inet Cam PSs100 System on my pc and install it again

I have
Change the hub(i have called it hub but its a linksys router )
disconnect the camaras one by one

i hope your help