Can't delete user backup files

In the user backup area there are about a dozen files (close to 1G). When I click on Manage Backup Files I get an error that says "Cannot read file ....."  When I click individually on the "Download" links all but one can be down loaded.  This file gives an error "firefox can't find the file ....." I assume this file is corrupt but it is causing major problems as the backup size is getting out of hand and I can't delete any of them

I am using v2.4.1 and am logged in as a full administrator.  I just ran cron.php and that made no difference.