Acronis 2012 cannot find source disk

I used ATI 2012 for years, including for the last ten months in this same machine, and never encountered any major issue, either backing up or restoring. As it happens now, I had uninstalled 2012 to install ATI 2015 three days ago. When I encountered some serious problems with 2015, namely, not being able to recover from rescue media, I decided to uninstall 2015 and reinstalled my previous 2012 product.

My problem now is when I start a backup session with my reinstalled ATI 2012, the box where the partitions on the source disk should be listed shows completely blank. Nothing is in there and no error message appears anywhere.

When I first uninstalled 2012 and then the 2015, I had read that a couple of Acronis processes should be manually removed using Task Manager, which I did in both cases. I ignore whether this may have had any bearing on this present situation. I use Firefox 32.0.2 on Windows 7/64.

Can anyone provide some guidance on this, please?

Edited to add that if I click on Backup Files & Folders the source disk shows up with no apparent issues. Also, in the destination box the Drive C: and all its partitions are always listed, together with the external drive where I store all my backups. Thought this might be important.

Still one more detail that may have significance: If I try to restore from the Acronis application, after choosing a backup to restore from, the screen for "Source and destination" lists all my SSD drive partitions. When I click on each small box for each partition, a new box opens underneath with this text: "Choose recovery partition." But when I click on it or on the down-pointed arrow on the right side of the box, nothing happens. After all, the partitions listed are supposed to be the destination, the source being the backup file in the external drive...

Guess I'm getting lost here...