Has anyone seen this? Know why it might be happening?
On my log import pages (happening on multiple sites), I'm seeing the same file entered twice, once with the Good Rows actually populated, once with nothing but a - (dash) in it. It's a single web server setup, not load balanced, so no chance of there actually being multiple files with the same name.
Looks like below (I'd do a screenshot, but I don't see how to attach it):

cccc.log    6/3/2015    330
cccc.log    6/3/2015    -
yyyy.log    6/2/2015    240
yyyy.log    6/2/2015    -
xxxx.log    6/1/2015    100
xxxx.log    6/1/2015    -