I have tried to start CMDBuild 2.4 in Mozilla Firefox 45.0.2 and the login window doesn't appear. The console writes (twice) the following message. In Google Chrome and MS IE 11 is it OK:
11:13:18.734 TypeError: CMDBuild.core.Utils.isJsonString is not a function
.decodeJson() Ajax.js:121
.adapterSuccess() Ajax.js:91
Ext.Function.bind/<() ext-all.js:21
.callback() ext-all.js:21
.onComplete() Ajax.js:196
.onStateChange() ext-all.js:21
Ext.Function.bind/<() ext-all.js:21
1 ext-all.js line 21 > eval:121:8
Thanks, Jiří