I had some issues that you've listed. In my case, was something with the version of Internet Explorer, in version 9 and bellow. With chrome and firefox everything was working fine.
We requested to our support team to update our users IE version to 10 or a newer, and it solved the problem.
After some time, we updated our Qlikview to SR7, and the errors that used to happen on IE9 disappeared.
So, try testing it on another browser, or in a different version of IE.
Hope it helps.