How to change IP address on printer…two show same IP

We have Lattitude D630 laptops, Lexmark C510 & T610 printers. When the teacher went to print the document wasn’t printing in her room but the one in the computer down the hall. The C510 & the T610 have the same IP address. I went into the C510 printer and changed the IP address in the printer but I can’t see the C510 printer when I type the “new” IP address into IE. When I type in the “old” IP address I am seeing the T610. Is there are way to force the laptop to see the new address. Am I missing a step to ensure that the “new” IP address is the true IP address…I read in another forum that IP addresses shouldn’t end in 0…and the “new” IP address does so could this be the real problem?