Multiple BES Servers - Blackberry Administration Service Error - The Application has encountered a system error...

I just finished installing BES 5.0.1 at the second of seven sites. I found that I was getting the error "The application has encountered a system error. Please report this error to the System Administrator. Please return to the home page or login again." when trying to connect to the Blackberry Administration Service (BAS) site and the BAS at the first sight reported the status of our second site as UNKNOWN.
Checking the log file I noticed the following error,

[com.rim.bes.bas.singletondeploymentbarrier.SingletonDeploymentBarrierManagerBean] [INFO] [BBAS-1011] {u=SystemUser, t=5936} isCurrentNodeTheSingletonInNewTransactionLocal CLUSTER:   heartbeat from another server (<SERVER NAME>) is still active, this server (<SERVER NAME>) cannot take over as singleton

You have to modify how BES pings sites. It needs to use TCP instead of UDP. Here's the article that explains how to go about fixing this error.

Configure the BlackBerry Administration Service instances in the pool to communicate across network subnets