Internet connection is intermittent, in an enterprise network

We are a small company with one router, one firewall, 7 servers (all run winows server 2003...we also have an exchange server--doing our users' email in house), and 110 desktop users ( all are win2000 or xp)...and at a specefic date (9 days ago), the internet connection has been really flakey.  Some users (about 10%) use their pc to connect remotely to data on servers hundreds of miles away, and most users (maybe 90% ...PLUS the 10% remote users) use various office applications --and all use their internet browsers to accomplish the majority of their work. Even the intranet applications are "showing" the
similar errors. When users can't connect, usually the browser (ie v 6) says "socket error", or sometimes the remote users' connection dis-connects, and they often can't re-connect (automatically or manually).

Things we've found out:
IF we go into the user's browsers (tools/internet options/connections the lan settings button), and click the proxy server is better...but all are still
un-connecting intermittently. We neverused to  have needed that "use a proxy server for your lan" checkbox checked.

There was a lightening storm last weekend...all problems appeared after that storm.

The users that login remotely to the offsite servers were the first to report the error. We contacted the sys admin dude there---and he said we are the only ones reporting any such connection errors. This sys admin says it looks like it could be our ISP...who we've contacted (not much help there).

We have reset the router (power cycled it), and re-configured the firewall (flashed it)...and checked all functions on the servers that we have.

Email seems mostly unaffected, although several users have the connection to our mail server conk out, lock up, or quit. . . but just for a couple of minutes.

Most of the errors show up on the browser connections.

Any ideas ? Thank you!

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I would start by checking the firewall and router for logs and see if there are errors reported in them.

It's possible if your building and equipment isn't grounded properly that either the router or the firewall got screwed up.

You'll need to try to determine which one it was (again by reviewing the logs on each).

If you are saying though that the internal users have problems connecting to internal resources as well (Exchange), then I would also check whatever LAN switches you are using for errors too.

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I suspect the switch between the router and the LAN is hurting.  Lightning is nasty.  I lost 2 NICs in 2 different servers one night - now I protect everything.

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Windows Server 2003

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