You shouldn't have to add everyone again. Have you ever used mods? Firstly, try disabling them just in case something is not working right (using the 'safe mode' launch button in pamm will do this). If you *haven't* used mods, I believe there is something integrated into the excellent 'PA:Stats' mod that fixes this issue (@cola_colin can give you more info). That mod also integrated a global chat into PA which is nice. To get that, go to the 'released mods' section of the mod subforum, and get 'PA Mod Manager' (PAMM for short). Then go to 'UI mods' and install 'PA:Stats'. I think that includes the tweak that sorts out issues with friend lists and stuff. I had this a while ago, however the list wasn't gone, just wasn't showing up.
I use this MOD,but it makes nothing to see for friends list.In fact,that MOD makes friends list and the notice list disappear.