Exchange users able to connect intermittently

I have about 35-40 users running on a Small Business Server running exchange. This morning we started getting issues with users connecting to Exchange. Some would connect just fine, others would not even attempt to connect. Some OWA access was possible, some wasn't. Then, if a user who was able to connect via Outlook closed outlook, then reopened, they couldn't connect. It's all very spotty right now.
I should mention that the server is at a remote COLO faciltiy on the other side of the city.

Things I've done.

1. Licensing, 37/45
2. OWA is accesible no problem from within the Server, no issues.
3. Server Reboot
...all among other things.

Any insight?

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Perhaps you have a bad primary DNS server and its correcting itself using the secondary?

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How is your connectivity to this colo? Getting any packet loss?
microsymplexAuthor Commented:
We got it figured out last night. Our ISP's DNS servers must have had an issue, and they reloaded an old database with our clients OLD IP address for the server. (It was an IP they had used a year ago) So depending on what DNS servers the clients were using, that was what determined whether or not they connected. We also got on the trail of DNS when you could go http://IP/exchange rather than http://server/exchange.
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