AFP and ethernet suddenly terribly slow

Hi,

I just got my brand new Imac 2.66Ghz and was in the process of moving stuff from my geriatric orange Imac G3 to the shiny new one.
Yesterday evening file transfers worked reasonably fast as in a few MB/s but today the max speed I'm getting is 80KB/S.
I see no changes in any settings. I've already rebooted both macs. Leopard was updated fully before I started transferring files yesterday and there haven't been any updates since.
I'm a little worried here because it does work. Now it's just terribly slow.

Can anyone point me in the right direction for a solution?

TIA!

edit: the transfer can only be done through ethernet over a hub that is also connected to a broadband modem. Internet seems to work fine. I think.
edit 2: internet is working fine

Amdahl said:

Could be a dodgy/incompatible hub or bad cable. Usually when I see this, it is a full-duplex/half-duplex mismatch issue. On some switches, you can force a port to full duplex, and it will then work at full speed.

Click to expand...

Nope, I'm getting pretty sure that's not the issue since internet actually works way faster over the same hub and cables. All ethernet settings have remained the same and the bandwith for AFP doesn't exceed 80kb/s.

Upon looking further into this on the interwebs it seems this issue is definitely software related and leopard specific. Especially when using airport, but apparently through ethernet as well.