Thanks for the info on the USB program loader. I've now got a copy of the Arduino cookbook which also mentions such things.
As to programme bugs, then if thats the case it must be in the libraries somewhere, but the problem of programme corruption is random in its symptoms but it happens after the mains has a funny five minutes - but not always.
As to the standard Uno having BOD at a lower voltage than the point that the chip becomes unstable, what were the people who design and build the things thinking of - not very good engineering in my book.