HTML Code:
<option value=$year selected="selected">"$year"</option>
More correct
HTML Code:
<option value="{$year}" selected="selected">{$year}</option>
Also it may be caused by duplicating options with the same value
F.e. if 2009 is selected you will get
HTML Code:
<option value="2009" selected="selected">2009</option>
<option value="2009">2009</option>
Try to use foreach or section cycle to output options