Really Slow Network Access in Homegroup

We have three computers all running W7 Home Premium set up in homegroup via a wired Draytek 2600G router.
Internet access for all machines is fast and reliable, and everyone can see every machine.

However, trying to transfer files via the homegroup is ridiculously slow, quoting hours for some things.
100/full duplex is set for all network cards, but I'm seeing speeds of 38k and the like :eek:

Any help appreciated.

There are no speed settings in the router, just QoS, and that's all off.

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