Single Version backup cannot locate archived backup file.

I am running Acronis True Image Home 2010 in a Windows 7 64 bit system. I am having a problem that is very puzzling. I run the Single version backup which means that it will first locate an archive on the disk then over-wite it with a new backup. What is happening now is that it cannot find the file in the allocated directory, it is looking in the correct location but the file does not exist. I just ran a backup yesterday along with a verify and all went well but today it can't find it as it is not there. I have no idea what happened to it. I did not delete it but it is gone. I then deleted the backup and created a new one with the same options. Thinking that this will be the first time for this backup and it knows that there is no archive it should run successfully but it still fails for the same reason, file not found. This has happened to me before and using this process has worked but not now. I just can't understand what is going on. There is over 698 gigs of space available on the disk which is a 750 gig expansion USB drive that is always connected. I actually run 2 backups of these files every time I make a change no matter how slight with the second to another expansion drive and it ran fine. Same backup options same files one right after the other.

I have attached the jpg screenshot of the log showing the error(s) as I tried running it several times.

Can anyone shed some light on my dilemma and help me solve this problem. I just don't have any idea how to proceed.

Any help will be appreciated.

Regards...............Ralph