When I turn my computer on, the 4 user names appear and i usually just click the account picture that i wiwsh to use. none of the accounts have passwords. now when i turn the computer on the user names appear but i cannot click on them. the cursor does not change when i hover over them and i cannot click 'turn off computer' either. i have to restart it to get it to work. this used to only happen from time to time, however it is happening more frequently. what is going on?