NW6SP3 with BM3.7SP2 patched as per Craig's site. This is set up to
connect
to an upstream proxy, currently configured as type CERN. This is a
Cisco
product but I am not sure which one.

We have started to receive a lot of 504 errors e.g. Load google and do
a
search. The first results page displays ok but if you click next to go
to
the next page you get the BM 504 error screen instantly. Press F5 to
refresh
the page and it loads instantly. This is not limited to google or
searches
but can happen at just about any site. Many pages take a long time to
load
but do eventually load. Links within these pages load very quickly
almost as
if one of the proxies is attempting to load the entire site before
delivering the first page. The Windows Update site will never load
despite
having been working fine yesterday.

We had this problem last week but it seemed to clear itself on Friday.
This
has reoccurred today. Speaking to the upstream admin he says there
have been
no changes to the setup at their end and I have made no changes at my
end so
am at a loss as to what might be causing this. We have both emptied
our
cache and rebooted but to no avail. These 2 proxies have been
connected for
several months and have not had a similar issue before last week.

To make matters worse there is a further upstream content filter which
has
had problems in the past over which neither of us has control although
this
is in the pipeline to be changed.

What tools can I use to find out where this error is being generated.
All we
get at our desktop is the standard BM error page but is this being
generated
from our proxy, the upstream proxy which passes it to BM which then
passes
it to us or further afield?

I realise this is a very loose question with many possibilities but
any
hints on beginning to track this down will be much appreciated.

Thanks in advance.