Are there any errors in the javascript console?
From FireFox:
--
(new TypeError("g.addr.substring is not a function", "https://blockchain.info/Resources/wallet/wallet.min.js", 1)) @ https://blockchain.info/Resources/wallet/wallet.min.js:1
From Chrome:
Uncaught TypeError: Object has no method 'substring' wallet.min.js:1
buildSelect wallet.min.js:1
buildSendForm wallet.min.js:1
$.on.FB.init.appId wallet.min.js:1
f.event.dispatch jquery.min.js:3
f.event.add.h.handle.i jquery.min.js:3
f.event.trigger jquery.min.js:3
f.fn.extend.trigger jquery.min.js:3
e.extend.each jquery.min.js:2
e.fn.e.each jquery.min.js:2
f.fn.extend.trigger jquery.min.js:3
buildSendTxView wallet.min.js:1
buildVisibleView wallet.min.js:1
$.ajax.success wallet.min.js:1
f.Callbacks.n jquery.min.js:2
f.Callbacks.o.fireWith jquery.min.js:2
w jquery.min.js:4
f.support.ajax.f.ajaxTransport.send.d