I added the points to line layers, the ones that wouldn't show up before, to a new map. The lines showed up this time. There are records and the information under the source tab does specify GCS_WGS_1984. There is a problem with the lines though, it is described below.
I downloaded the zip file you included and tried everything you said, and it all worked. So the tool must be working.
When I look under the "Help" and "About ArcMap..." It says that it is ESRI ArcMap 10.0 and farther right in parentheses it has (Build 2414).
I tried adding data again, out of curiosity, to see what would happen. Surprisingly, I got a different result. Each time I add data and use the points to line tool (I have done this several times tonight, but only tonight) the tool runs and gives me an output that appears on the screen without the program shutting down. But this output is not what I expected, I'll attach a screen shot so you can see, but there are several horizontal lines running across the map, which I know should not be there. The number of lines, and the placement, differ with each month and year I work with, but the same types of lines always appear. I'm not sure what is causing this, because it has not happened before (except when I added the lines which didn't work before to a new map document).
I have attached a screen shot of the output of my data and the excel file that goes with it.