It will be a local network issue rather than an ISP issue - also check that you have not created a double NAT configuration with the Time machine box. I am not directly familiar with the device, however, if it is basically and Airport Extreme/Express with a hard disk attached, then definitely make sure that its router functionality is switched off and you are using it in bridge mode.

John

808v6, M60, MC200, HD621, Lumagen XE, 504, SB Touch, 563, 201, 204, 208, MPMAX 221, M80, Explorer, Explorer2.