Form is missing _ token _ or it's fields

I choose to uninstall from the control panel of my hosting after repeated failures unsuccessfully upgrading the software from my hostings 1.8.15 offering to the 1.9.7 release.

Now I want to just stick with what was working, the 1.8.15. The uninstall was reported success in control panel, however some files were left behind so I deleted them before issuing a new instant of 1.8.15 through my quickinstall panel from hosting.

I am getting the error: "Form is missing _ token _ or it's fields" when logging in.

Did I need to take a different approach to uninstalling?