I can click on the image but not the caption
If like me you have your WordPress system configured to report all messages
then you have probably seen this message from oik-nivo-slider version 1.2
Notice: Undefined variable: oik_nc_script in oik-nivo-slider\nivo.inc on line 163
Because the variable is not set then the jquery.oik-nc-click.js jQuery code will not be correctly added to the page so the highlighting of the caption will not be performed when it’s hovered over.
Sorry, this will be fixed in the next version.