Access denied exception when launching InternetDriverServer (C# Selenium)

Hi, 

I've read numerous threads and posts regarding this issue experienced by many users, but have not found a solution. 

When I launch my test it runs to the point where it attempts to launch the instance of the IEdriver :

Instance = new InternetExplorerDriver(@"..\Documents\Visual Studio 2012\Projects\Drivers");

The following error is displayed: System.InvalidOperationException: Unexpected error launching Internet Explorer. IELaunchURL() returned HRESULT 80070005 ('Access is denied.') for URL 'http://localhost:50622/' (NoSuchDriver)

I tried modifying my Windows mgt and instrument. properties per other posts, but have not resolved the issue.

*Interestingly, the issue occurs frequently , but not on every test run. It may run successfully twice, then throw the above exception on the next launch. 

Any ideas as to how to resolve this issue?