ping packet loss when size gt 1500

[Adam Hardy <adam.ant@cyberspaceroad.com>]

I thought I knew enough to keep my own home LAN going but I'm stuck on this one 
and I can't work out what to do next. In fact I thought everything was fine 
until I tried pinging with big packet sizes.

ping -s 1472 www.bbc.co.uk
ping -s 1472 208.245.107.9

works fine, no packet loss ever.

ping -s 1473 www.bbc.co.uk

works fine too.

ping -s 1473 208.245.107.9

results in 100% packet loss.

I have a bizarre problem with the server at 208.245.107.9, which is an internet 
broker whose server keeps disconnecting when making data requests. Their support 
is blaming the problem on me.

208.245.107.9 is used by a huge number of clients and I apparently am the only 
one suffering.

Could it be something on my LAN? Or could it be my ISP (British Telecom) whose 
DNS server will randomly go down for a while and then come back (not in sync 
with the appearance of this problem though) - I thought I'd state that to give 
an idea of the ISP's reliability.

Or is this ping problem definitely something I can sort out and perhaps solve it?

Thanks
Adam