Dennis I had a similar issue with my Lexus last year, about the same vintage, Lexus wanted $350 for an up to date disk. I had a sniff around a few GPS and Lexus forums and found that I could download the data file and burn that on to a DVD, needs to be done a certain way as it's an .iso file. Fixed the problem instantly and for the cost of a blank DVD and a bit of time.
I'd come help you out myself but as I'm in Australia it'd be a bit of a trek. However, I will have a look around and see if I can find the file for you. Any 15 year old should then be able to help you out with the rest.
Updated. Have a look at this link
http://www.satnavdisc.co.uk/index.ph...product_id=287