Alas, things were not that simple, after all. Looking at the registry on a different machine, I determined that the filter added to the DVD/CD ROM drive registry entry might have been one added by iTunes and is needed by it.
I say maybe because I did not make careful note of the one that I deleted on the machine that was having problems with Acronis starting.
I tried accessing the CD drive from iTunes and it failed, telling me that there was a registry problem. So I did a “repair” install of iTunes and then iTunes was able to access the drive. And Acronis still loaded.
I’m thinking that perhaps something corrupted the iTunes CD “driver” and the failure of Windows to access the drive was what lead to Acronis hanging on startup. Deleting the registry key fixed the CD drive access problem which fixed Acronis, but perhaps “broke” iTunes. The repair install with iTunes fixed that, but because it was a true “repair” it didn’t cause the original set of problems.
I don’t really know what was going on, but it seems things are back to the normal state.
