EVOVI

We have had BT yahoo ever since we got broadband but yesterday we got a strange problem with the bookmarks.I was logged on and my bookmarks were all there,I logged off and my dad logged on and my bookmarks were there in the drop down menu.If you click edit bookmarks his bookmarks appear.Now this morning it is the other way round I have his bookmarks showing..
Anyone else had this happen and is there a way to fix it..
Cheers