Having problems when uploading a Sitecore Package from one environment to the next. Both environments have the same version level (Sitecore XP 8.1U3 / EXM 3.3).

Screen error message reads:

    [NullReferenceException: Object reference not set to an instance of an object.]
       Sitecore.UIUtil.GetBrowserClassString() +347
       Sitecore.Shell.Controls.Standard.FormPageXmlControl.OnLoad(EventArgs e) +1154
       System.Web.UI.Control.LoadRecursive() +67
       System.Web.UI.Control.LoadRecursive() +164
       System.Web.UI.Control.LoadRecursive() +164
       System.Web.UI.Control.LoadRecursive() +164
       System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +4497

Sitecore Log Output:

    3028 15:10:20 INFO  File has been uploaded: D:\inetpub\wwwroot\Sitecore\Data\packages\ClientMailCoreSpeakApplication.zip
    ManagedPoolThread #5 15:10:25 INFO  Job started: Install
    ManagedPoolThread #5 15:10:25 INFO  Installing package: D:\inetpub\wwwroot\Sitecore\Data\packages\ClientMailCoreSpeakApplication.zip
    ManagedPoolThread #5 15:10:56 INFO  Installation was aborted at entry: items/core/sitecore/client/Applications/Client Mail/{B1F6C86A-4F1D-4A60-8949-EC945ABE0675}/en/1/xml
    ManagedPoolThread #5 15:10:56 INFO  Installation was aborted
    ManagedPoolThread #5 15:10:56 INFO  Job ended: Install (units processed: )

> Note that the Sitecore log does NOT show the 500 error displayed to
> the browser.

[![enter image description here][1]][1]

### Process:

 1. Upload Package File - Successful.
 2. Click through to Name and License Dialog - Successful.
 3. Clicking the **Install** button immediately throws an error.

### Package Contains:

Contains Sitecore items meant for the core database to install a new Speak Application.


  [1]: https://i.sstatic.net/KgCe6.png