"Not opened for read" error

I just downloaded and installed the program. I am using the trial license. I opened a .dwg file that I created in AutoCAD Map 3D 2011 (basically an AutoCAD 2011 file). When I attempt to do anything I get errors. Trying to use the offset command (typed or from the icon) I get "Not opened for read" and I am returned to a blank Command: line. I get the same error when I click the polyline icon to draw a polyline. Lots of other commands produce this same error. Then I try the copy command (from the icon) and select objects to be copied, but when I click the right mouse button to finish the selection I get "Invalid input." Interestingly, I can use the multiline command. I'm wondering if the trial is actually that limited? It's pretty difficult to the program if I can't draw or edit much of anything.