I have found the free software TCPOptimizer (available at http://www.speedguide.net/sg_tools.php) to be quite useful for maximizing the upload and download speeds for all of my PCs (Windows XP, Vista, and Windows 7 among the bunch that I own).
You need to run the software with Administrator privileges for the optimum settings that the software selects to "stick".
What I understand from your post, is that you're having issues with the Slingbox streaming from a remote location.
In this case, what I would recommended, is to discard any streaming restrictions from your IT Department, try hardwired connections between the Slingbox and router and check the wireless settings.
Besides that, you can try to connect from a different network to discard the current one as a potential issue.
Also, make sure that you're using a hardwired connection between the Slingbox and router and try to use a different port during the Internet Viewing as well.