Javascript errors

Hi,

I believe javascript errors are causing various problems on my website. Specifically in the admin section, when pressing buttons that typically bring up a lightbox, the screen simply jumps to the top.

Here is one of them:
`Uncaught TypeError: Cannot read property ‘hasClass’ of undefined load-scripts.php?c=0&load%5B%5D=jquery-ui-draggable,jquery-ui-droppable,jquery-ui-slider,jquery-tou…:1043(anonymous function) load-scripts.php?c=0&load%5B%5D=jquery-ui-draggable,jquery-ui-droppable,jquery-ui-slider,jquery-tou…:1043m.event.dispatch load-scripts.php?c=0&load%5B%5D=jquery-core,jquery-migrate,jquery-ui-core,jquery-ui-widget,jquery-u…:3r.handle load-scripts.php?c=0&load%5B%5D=jquery-core,jquery-migrate,jquery-ui-core,jquery-ui-widget,jquery-u…:3m.event.trigger load-scripts.php?c=0&load%5B%5D=jquery-core,jquery-migrate,jquery-ui-core,jquery-ui-widget,jquery-u…:3e.event.trigger load-scripts.php?c=0&load%5B%5D=jquery-core,jquery-migrate,jquery-ui-core,jquery-ui-widget,jquery-u…:8(anonymous function) load-scripts.php?c=0&load%5B%5D=jquery-core,jquery-migrate,jquery-ui-core,jquery-ui-widget,jquery-u…:3m.extend.each load-scripts.php?c=0&load%5B%5D=jquery-core,jquery-migrate,jquery-ui-core,jquery-ui-widget,jquery-u…:2m.fn.m.each load-scripts.php?c=0&load%5B%5D=jquery-core,jquery-migrate,jquery-ui-core,jquery-ui-widget,jquery-u…:2m.fn.extend.trigger load-scripts.php?c=0&load%5B%5D=jquery-core,jquery-migrate,jquery-ui-core,jquery-ui-widget,jquery-u…:3(anonymous function) load-scripts.php?c=0&load%5B%5D=jquery-ui-draggable,jquery-ui-droppable,jquery-ui-slider,jquery-tou…:393j load-scripts.php?c=0&load%5B%5D=jquery-core,jquery-migrate,jquery-ui-core,jquery-ui-widget,jquery-u…:2k.fireWith load-scripts.php?c=0&load%5B%5D=jquery-core,jquery-migrate,jquery-ui-core,jquery-ui-widget,jquery-u…:2x load-scripts.php?c=0&load%5B%5D=jquery-core,jquery-migrate,jquery-ui-core,jquery-ui-widget,jquery-u…:4b

Please help?