DW web site not viewing properly under Vista

[ja...@fornobravo.com]

I have a web site that passes validator.w3.org as 4.01 Transitional,
along with the DW validator and a third-party HTML validation tool
(HTML Powertools).

In the past few days I have heard from a couple of Vista/IE7 users
that some pages do not load correctly. The site is a couple of years
old, and we have not had any problems before.

Any ideas on what I am doing wrong? What is a good tool to use to
check my HTML against Vista and IE7?
Thanks.
FB