The XTB-IIR shuts down its transmitter when there is excess X10 traffic on the powerline. That is usually caused by a stuck transmitter, such as setting something heavy down on a Palmpad.
The default will pass a burst of about 120 commands, or 20 per minute continuous. Selecting the high threshold will pass a burst of about 400 commands, or 60 per minute continuous. Note that many X10 operations require two commands - one to select the device, and a second to tell it what to do.
Here the default works fine even though there is a long macro that initializes everyting to a defined state when recovering from a power outage. However, devices that virtually saturate the powerline with commands, such as the burglar alarm interface, will eventually reach even the high shutdown threshold. The repeater configuration should be used for devices like that so they will continue to operate the subset of devices they can reach barefoot when the XTB-IIR eventually goes into command storm shutdown.
Jeff