This is currently a problem with lots of webpages. The problem is caused by the flash plug-in (here the clock). That ActiveX component has to be activated first to use (silly...). But I haven't seen this kind of effect before (looks like lightning, doesn't it...). It affects only Internet Explorer and Opera (at the moment). More information can be found here:
http://en.wikipedia.org/wiki/Eolas#Browser_Changes