Hi everybody,
I need help because sincerely I don't know where else to
investigate...

Environment: 2 BM 3.7 sp2 on NW 6 sp3 servers. CACHE ONLY servers
BM1 is on the inside (there's a firewall with DMZ configured) and BM2
is
on the DMZ.
Internet connectivity from both servers is good. Naming resolution
also.
The static routing and the DNS in Inetcfg is configured well. I can
ping
by name and by address everywhere with no problem.
On BM1 (inside) Cache Hierarchy Client is enabled and it is forced to

'Must Only Forward From Hierarchy' so that from BM2 server.
BM2 is configured of course for Cache Hierarchy Server and in its ACL
it
has BM1.
The only proxies enabled are HTTP, FTP and DNS

It happens that randomly surfing somewhere the users receive the BM
error
message "502 BAD GATEWAY - DNS NAME SERVER IS UNREACHABLE". Refreshing

the page two or three times it loads.
In the same moment of the client error on BM1 (the hierarchy client) I

got a console message stating ICP Parent(s) not reachable.

Any idea?