IE rendering of slideshow - some users see it, some don't

Test site: http://westwebtest.com/u3am

I have a slideshow in #header. This has another image of text overlaying it. It seemed to be working everywhere. I went live with the site and the client reported that she could not see a slideshow, only a series of images one under the other. I re-checked and now I couldn’t see it either. So I substituted a static image on the live site while trying to fix it in the test site.

I asked the slideshow author overseas to have a look and he said in IE he can see it playing perfectly. So I went back to my IE (I have IE 9 and IE 7 on different computers) and spent a while clearing the cache, temp files etc. After several go-rounds now I can see the slideshow working in IE. My client still can’t see it.

I have used this same slideshow on several sites and they are fine in IE. Is it just a matter of clearing the cache? I am reluctant to put it live again until I can work out why some people are not seeing it.

Thanks!