repair installation of MSXML or simply run the repair install for backup exec from add-remove program ...(repair install for backup exec would need a reboot)
Maybe you removed some temp files, It happened the same thing when something has been deleted in the IE temp folder.
fyi, I run a testing job and result is ok.
I did test to reproduce this issue, createe a new job , run this job , deleted the temp IE files in local session.
Check the database consistensy, if it gives the error then there is problem with thr database.
Run the databse repair or recover.
restart the sql(bkupexec) service.