all tabs disappear

Hello,

Since several months I had the experience that when I open a new tap, all my open taps, sometimes perhaps 25, are completely gone. Spend a lot of time in search and then I lose everything. Did not find a way to restore, sometimes I could. How it happens and how to do? It is more or less from the time that there is a special sign left from my toolbar and since that sign is there very strange things are happening. Is there a solution for it. Since this sign is there evrything becomes complicated. Thanks for hel in advance. Theo