This problem is easy to fix, the Task Manager is running in "tiny footprint mode". To correct this, simply double-click on the border around the window and it will return to its normal state. To place task manager back in "tiny footprint mode" again, double click again on the border around the window.
The tiny footprint mode allows you to resize the window to small sizes, bypassing the 'default minimal size' that occurs when you attempt to resize the window with the menu bar and tabs."