Microsoft Knowledge Base Article 305813 contains the following summary:

In Windows Clustering for Windows Server 2003, you can change the Cluster service account password on the domain as well as on each local node without having to take the cluster offline. If multiple clusters use the same Cluster service account, you can change them simultaneously. In Microsoft Windows NT 4.0 and Microsoft Windows 2000, to change the Cluster service account password, you have to stop the Cluster service on all nodes before you can make the password change.

To change the password for a Cluster service account in a Windows Server 2003 cluster, the following requirements must be met:

Mixed clusters with Windows 2000 are not supported; All nodes must be running Windows Server 2003 or later.
All nodes must be using the same domain account for the Cluster service.
All nodes must be online or in a paused state.
The update mechanism is not transactional; If the password change is not completed on all nodes, there may be a partial downtime in getting the passwords updated.
You must be logged on to an account that has domain access to change the Cluster service account password on the domain controller. You must have local administrator rights to each node to change the Local Service account passwords. This account must also have the ability to traverse directories in the cluster domain. ( Note : This privilege is given to every user in the domain by default.)
This article applies only to the changing of the Cluster service account. If other services are running under the same Cluster service account, you have to change them manually.