When I export to a text file, some lines end with * - which seems to mean no response. I also get a few that end with N/A. What does that mean?
The * indicates a lost packet.
The N/A means that that router wasn't participating in the route at that point.
Because of the limitations of text files (and the tools you're probably trying to import this data into - like Excel), only a single route is listed, and then the data is all printed with respect to that route. Sometimes, this means that there are routers in the collected data that aren't in the route you had selected when you export.
Usually, the best way to do an export is to set up your graphs so it's focused in on the period you're interested in exporting - and then making sure that you have the right route selected for that (version 2.30.1 and later help you do this by automatically selecting the most current route for the time period you have selected). Even then, though, only a single route can be used in an export, so if you have a bunch of routes in your data, the export will exclude some of this data.
Now, if you really don't care about route changes, but really care only about your final destination (you're planning to do an export) there are ways to get rid of the N/As and to combine data collected by multiple routers (at a particular hop) into a set of data that can be exported. This is done by setting up Ping Plotter to ignore some of the internal route changes. You can either do this for specific router groups, or just say you don't care about anything except for the most major (i.e. changing lengths) route changes by putting an "ALL" in for the exclusion list.
Another opportunity for N/As to show up is when you snap a "Copy as Text" when you're still in the midst of a trace. There might be some outstanding requests out there that just haven't had an opportunity to respond yet. Because we don't know yet. They're not time-outs, so we show that as N/A.