SBS 2003 Server occasionally not responding to some clients

I have a recently installed SBS 2003 server. In general it's working
fine. Exchange is working well, it's talking with the other domain
controllers etc.

Some client machines though it simply doesn't like for a while. e.g. I
plugged my laptop in to the network after bringing it in from home
this morning. Outlook couldn't connect to Exchange. Pinging its IP and
it didn't start responding until about 25 non-responsive pings had
been sent then it all went good and Outlook was able to connect.
Another desktop on the LAN did something similar but needed less lost
pings before it worked.

The network is good. On my laptop I was able to ping my desktop and my
desktop could ping the server. It's all one big LAN segment. It seems
that pinging it sometimes gets it going.

Other client machines are unable to just use IE to access Outlook Web
Access.

i.e. the server basically ignores some clients completely and some are
just fine. Then the bad clients sometimes magically come good. It
sounds like networking hardware but I'm sure it's not. Everything else
is working fine. It could be taken as firewall like behaviour. The
server firewall is definitely off.

Any ideas?

And that's SBS 2003 R2 SP1

On Mar 22, 3:36 pm, christianh...@gmail.com wrote:
> And that's SBS 2003 R2 SP1

Further to this. On 2 out of 3 machines today it took exactly 25 non
responsive pings and then all of sudden the server started responding.
The 3rd machine took 29 pings before it worked.

I have no idea what this could mean.