I indicated that the monitor was going off on its own at various times. It seemed logical that the first thing to consider was the 150 watt transformer. Anything else would require bringing it in for repair at a high cost. I therefore purchased the transformer directly from Apple after a helpful conversation with Apple support. The transformer cost was half of what it would have been if purchased on-line from someone other then Apple. Well it seems the new transformer has solved the problem. So anyone out there who has experienced the same problem with any Cinema Display consider replacing the transformer.