Fatal errors regularly generated by WP and related to Visitor Statistics

Started getting email messages about problems with this plugin more than two months ago, less than a month after installation. Initially I ignored them as I was trying out the plugin, particularly since the error messages seemed mostly (but not only) to be related to ajax. Logging out each evening from the admin view worked for a while, but now the problem is back, on a daily basis, regardless of whether i’m logged in or not. I can’t help but wonder if it’s the free version that’s screwed up on purpose (and I should add that I was about to actually pay for the upgrade but wanted first to confirm that it’s working as it’s supposed to), just to move everyone towards the upgrade, or if the developers are getting careless!