Why is RPM not collecting data all of a sudden?

Last night I set up New Relic RPM (free version) on a Rails production website and initially data was being collected fine, stats were generated, etc.

However, now it appears that data is not being sent, and I get the following error message in the New Relic log from last night:

[10/09/08 20:10:49 (15188)] ERROR : Error communicating with RPM Service at collector.newrelic.com:443: Connection refused - connect(2)

I restarted by Rails app about 20 minutes, ago, but data still isn't being collected, according to my RPM account.

The New Relic log shows the following since the app restarted:

[10/10/08 10:06:53 (15920)] INFO : New Relic RPM Agent Initialized: pid = 15920
[10/10/08 10:06:53 (15920)] INFO : Agent Log is found in /home/user/apps/application/releases/20081006040602/log/newrelic_agent.8010.log
[10/10/08 10:06:53 (15920)] INFO : Runtime environment: Mongrel
[10/10/08 10:06:53 (15920)] INFO : Transaction tracing is enabled in the agent
[10/10/08 10:07:06 (15920)] INFO : Connected to NewRelic Service at collector.newrelic.com:443.
[10/10/08 10:07:09 (15920)] INFO : Transaction traces will be sent to the RPM service
[10/10/08 10:07:10 (15920)] INFO : Reporting performance data every 60 seconds

Any thoughts on what might be going wrong or how I can get more information?

Cheers,
James