Well, i supose you all used the encryption thing right? There has been problems with the that and people accessing it. I read in one thread that patchou will be fixing this in an update. And until then, all you can do is uninstall plus! and reinstall it (without saving preferences while uninstalling) Until this is all worked out, i would recommend hiding your "my chat logs" folder by right clicking it>properties> and check hidden. To make sure people dont see the folder, tools(top of page)>folder options>view> "Hidden files and folders." This is, if you dont want ANYONE to access them.
***If you uninstall plus! you will lose all your chat logs that were encrypted***
Hope that helped