I would guess the network you are accessing is blocking ports 7578 (KVM), and maybe 5120 (CDROM redirect) & 5123 (Floppy \ USB redirect)
This it the tool i use to check open ports to the network. Advanced Port Scanner 1.3 (Free) - Small, fast, robust and easy-to-use port scanner for Windows which uses a multithread…
I find I need to slow the tool # of threads to keep it from erroring out on a high speed network,