Let me thank you for your attention to this point. It's greatly appreciated.
After recursively changing ownership of all files and directories to my user and group, still no success with the uploader. I am baffled and frustrated...
I can only imagine at this stage that perhaps I should look at replacing a few files? Or if it's possible to know which files are needed specifically for the Flash uploader to work, what the RWX permissions need to be? I've had a couple of plugins report over the past couple of days that their directories weren't writeable, so I think the install from MediaTemple may have some restrictive permissions on directories by default.
Again, and further insight is greatly appreciated.
Cheers.