Sounds like the column got stuck at being a really large size up and down. I tried to replicate your issue (to an extent) by intentionally increasing the size of my parameter dial bar past the taskbar, and I ended up having the same issue as you, where I was unable to reach dials past a certain point.

What I tried as a workaround was this. I started dragging the parameter dial bar upwards a bit (it won't let you do it very far) but when you do this, it slides that window up, and then snaps back down. If you continue to do this, you can eventually bring the bottom of the parameter dial bar above your taskbar.

Of course, you could alternatively just set your screen resolution for something crazy high temporarily, and resize the bar, and change back to your normal resolution.

 

Currently using Poser Pro 2012 (Display Units = feet)

AMD Phenom II 3.2ghz (6 cores)

8gb RAM

Windows 10 Pro 64bit