First of all, I am not quite sure if this is an Creo or an Windchilll issue.
After upgrading from Windchill 10.2 to 11.1 there is a little grey box within the preview of the part (embedded browser).
It also does not seem to depend on the version of installed Creo, because this effect is visible from Creo 3 to Creo 5 (also tested on several machines).
The same page works perfect in Firefox, Chrome and even Internet Explorer.
Thanks in advance.