I attempted to make a backup of OS partition and got the following message:
Modification has failed: no task to modify.
More information about this error and solutions may be available online in the Acronis Knowledge Base. To access the online resource manually, enter the event code at: http://kb.acronis.com/errocode/
Event code: 0x00090063
I ran a search by the above code but could not get any hit.
Edit: The problem has been resolved.