What release of Project? What service pack do you have applied? Project 2007 is up to SP-3, Project 2010 is up to SP-2, and Project 2013 is up to SP-1.

When you say you enter "data from .5 to 5 days per week for each task" - I assume you are entering work in the assignment row in the Resource Usage view? If you zoom in do you see the hours per day spread as expected? If I enter work per week - unless I am using Fixed Duration tasks, the task duration shortens when I enter 4 hours (.5 days) of work on a task in a week.

In testing with Project 2010 and manually entering the work on the assignment line - the weekly values match the default Baseline Work Visual Report.