[vista]your windows defender has stopped woriking

1.gw pake vista,pas masuk windows, di desktop muncul tab"you windows defender has stopped workin"....

2.trus klo gw pake beberapa program, misalnya windows photo gallery..
tiba" muncul tab "windows explorer has stopped working, windows is searching the problem"

kenapa gitu kk?, gw tiap hari update windows gw padahal, trus notebook gw juga web-camnya g bisa dipake,waktu baru beli kan masih XP, trus gw ganti vista... langsung banyak kecacatan terjadi...

tolong solusinya kk