Sounds like you did a pin reset (paperclip in the hole in the back?). Try a full factory reset (you'll lose your settings etc). I can't remember on the wifi if there is an option to do that in the settings menu or not (check there). If not search the forums for factory reset. Sorry I can't remember what the buttons/sequence is for the wifi.
The problem you are describing sounds like a database corruption issue, so factory reset might be your only choice.