Only the newest version of Opera shows the issue. It seems that Opera doesn't like the ticks. If setting tick as 0 in esri.config.defaults.map.sliderLabel, it works fine. Of course, that would lose the ticks. Please add the following code to the init() function:
if (dojo.isOpera) {
esri.config.defaults.map.sliderLabel = {labels:null,style:"width:2em; font-family:Verdana; font-size:75%;",tick:0};
}
Hope this helps.