Cant customise site title,tagline, navigation, front page

Everytime i try to edit my site title , Appearance > Customise , the options in the side bar do not load properly and i am unable to change anything (having to press the exc keyboard because even the close or save options are unclickable.. i have tried on another computer, have upgraded my wordpress and still am unable
Any help is greatly appreciated.. who can i ask about this ? i have contacted my theme support and they say its wordpress – and it doesnt seem host related ? not that i would know ? thankyou