No Calendar icon from a JavaServerPage using OperaMini

Hi all!
Using OperaMini browser at my mobile phone and accessing to my JSP Webpage with a calendar component (field+icon), when pressing the calendar icon, a calendar should appear to choose the day.
The problem is the calendar icon never appears. (but the area is there. If pressed it opens)
Using a PC browser it works without problem.
Does anyone knows how to resolve this ? Can it be a OperaMini bug or some Lib at server site that is missing?