I have a W2K server in a NT domain, running DNS, DHCP, WINS plus file
and print services. Over the last few months I've been experiencing
drop-offs from the network for this server. It's still pingable, the
DNS can still be queried fine, but the NetBIOS connectivity is gone --
no browsing it, no drive/printer mappings resolving.

I thought this may be a goofy master browser issue, we've had some
issues before with switches not behaving correctly (spanning tree
algorithm issue) and the master browser getting lost on NT servers,
but nothing has affectyed a W2K server before and using BROWSTAT
doesn't reveal any problems until it loses the NetBIOS connection,
then BROWSTAT shows it can't find the master browser, presumably due
to the lost connection.

I'm running out of potential culprits in this and potential fixes.
We've updated all securtiy fixes and service packs, reloaded current
NIC drivers and so on. Sometimes it appears to be fixed, but this is
an intermittent problem, happened three times on Friday, none since.
No error log messages except related to having already lost

So, any suggestions where to look next?