You are getting the status File/Object not found because of the new process in the scan engine of version 5.
When scanning multiple files/objects (like the hard drive, or a directory), the scanner will collect all results from all files/objects scanned and report the most critical. If you scan 100 files and 99 are ok, but 1 is not good, the result from the scan engine most likely will be the error from this one file.
This is one known issue with the version 5 engine – if an access to a file is denied, there is a high chance that the scan engine will report that as "object not found", especially if it can open a handle to the file and later can't read from it. The most likely reason for seeing this message is that the scan engine tried to scan files and was denied access to them (during open or read), but reported them as "not found". Even as administrator, when you scan the system hard drive and windows folders, there will be many access denied files (some of them in use, some of them protected by the operating system).
We will try to solve this in the near future by improving the error collection mechanism and providing a more intelligent way of detecting what the most critical error should be during scanning of multiple objects, right now it is very simple, all errors have "weights", the error with the most weight is reported, and "can't read from file/not found" has one of the highest priority codes, the trouble is that it is very likely that you will always see this error when you scan your system drive.