Problem with viewing in IE7

One of my clients is having issues viewing our courses in one of their offices on IE7. The course freezes on the grey progress bar and the only way to progress is to relaunch the browser, deleting the temporary internet files each time, and try again.

We've checked Flash is updated, internet connection speed is fine, etc. The course works ok when tried on IE8 and other browsers and is also fine for all their other offices, which have the same group IT policy. There seems to be something somewhere in that office's particular network that is stopping the Articulate content displaying, but I don't know what!

Has anyone else had any problems with IE7 in particular, or have any ideas what I can suggest might be preventing the courses launching?

Thank you,

Louise