Thanks for the comments. I see that Steve Dale has just posted about this issue. Communities and Collaboration – Say No To Internet Explorer 6 (IE6)
http://steve-dale.net/2010/01/31/say-no-to-internet-explorer-6-ie6/

The probable reason why the third party suppliers haven’t moved off IE6 is that it costs money to undo the special adaptions which they had to make in the absence of any standards compliance in IE6.

This is an object lesson in why software suppliers should follow international standards rather than promote their own proprietary ones.

We can specify that new software procurement will use a modern web browser and ask our existing suppliers to provide upgrades that do not need IE6 but In the meantime we have to put up with IE6′s security vulnerabilities and inefficiency costs.

I am not surprised. That’s the other excuse I am often given – “We have to use IE 6 because we are still running Windows 2000/2003″. But 2000 on local government systems is seriously scary. If you wrote a novel about hacking around this it would not be believed. You couldn’t make it up as they say. But if it’s good enough for a major international investment bank, it’s good enough for RBC. Totally irresponsible.