With Macromedia ColdFusion MX 6.1, if a data source is configured to maintain connections and the number of connections are limited (under Advanced Settings in the data source), it may cause the server to hang when trying to get a new connection, particularly if the server is under load.
You'll find a hot fix for this issue here, as well as more detail and explanation about the issue.
ColdFusion MX 6.1: Hot fix for Data Source Connection Pooling