Windows XP SP2 Log on issue?

hi guys, since saturday, ive had a strange problem, when i get to my login scereen, i log on as usual, then windows starts fine, all my sys tray loads until it gets to the windows red security sheild......at this point if i go to task manager, it doesnt say im logged in as anyone..there are no users there, this is a problem, mainly as now my network to my router wont appear and i cant get on the net.

i have noticed that if i click start and right click over my computer and go to properties....after around 4 minutes, my screen sort of refreshes, then it all appears normal, but it is definatley when the security center starts up, any way of getting it out of my sys tray on start up, simply turning it off has done nothing!