I go into the Plugin and try to Install Plug in from the tab.
It toggles to Browse.
Click on Browse and it toggles back to Install Plug in.
Ie it is not actually allowing me to get to where I have downloaded a previous version of the MarketPress plug in so I can roll it back.
Why it is not letting me browse to my own folder.
It is just going around in circles.
The access is available if you want to take a look.