From the first partial picture, you have option switch to Single user mode, if you login as multi-user mode, you wont able to backup, you can login as single or switch to single user mode to create backup.

for second issue, I would recommend you check the sample see if you have the same issue, if sample is good, then this could be a data issue.

if you have 2007 version, you can go to maintenance try run advance database check