NO visitors for 6 months... (no replies)

Well, back in February-March, the four websites Piwik monitors on my Windows webserver stopped getting any hits. The visitor log stops March 4 on one of the websites. I've been updating Piwik when updates come out (Well, I wait a month or so to make sure it's stable), and I'm currently on the latest. I'm not sure where to start. I suppose I could wipe it out and reinstall, but I'd like to at least try and salvage any existing statistics. I didn't make any changes to the websites (Certainly not all of them at the same time), and didn't make any server updates.

Any ideas?

Thanks!