Thanks for the info inplainsite.
However, in trying to explain to the customer that all our tests on different browsers were not showing any problems, I could not satisfy her with us not having any tests on Vista platform. It would help me to be able to explain to her it really is most likely her computer. Not that she will accept that either because ours is the only site that happens to her on, and only on that page so from her viewpoint it is something wrong with our page.
Anyway, I'd appreciate any verifications and other insights.