I have just installed firmware 3.3.3 RC4 Beta and things have improved. I can now connect a usb disk without the dsl connection dropping off. I can also write files to the public folder on it, but if I try to browse the files using the vigors browse file function (New command to this firmware version) the router reboots. Also when I set up a new share I am unable to access it via samba as the password is not recognised.
Not fixed yet but definately getting better.

Update: I got my money back, and will continue to follow progress on the Forum. I'll consider purchasing when the dust has settled.