Quick follow-up: The logger ran flawlessly for 60 hours over the weekend and the RTC didnt lose any time. I forgot to take a voltmeter over to that lab so I couldn't check the battery. Doh^10
Can the serial connection override the processes of the Arduino? InBetwino is really laggy and after 24 hrs it is 3hrs behind in writing to text file. Its still in beta though. I just wondered if the lag from InBetwino can feed back into the Arduino's processes. I've moved to HyperTerminal for PC-based logging to text file instead of InBetwino. No lag encountered. Splendid.
BTW, isn't HyperTerminal the most inappropriate name for such a gods-awful piece of crud program? It sounds like it should be the name of the next cutting edge mobile handset.
Thanks for all the replies, kids!
Le Scare
postscript: just checked the voltage: 3.2. Probably not a flat battery then. Odd as I thought I did a pretty good job of soldering it together. Will have a look to reassess.