Connectivity with crossover cable but not via switch

Hi,

I have a device which I can access from my PC when connected to it via
crossover cable, but if I connect it through a switch then I can't
access it from the PC. However if I replace the device with another PC
then I can access this second PC OK.
How is possible that the device, which used to connect without
problems in the past through that switch, now can only be accessed
through a crossover cable? The device is very simple and just allows
to set it's IP address and port. I also have tried to connect the
device to the switch with crossover and straight cable without
success.

Thanks and regards.

Santi