This usually means the inventory service failed to connect to the database. Could be due to an interrupted connection, a time-out, etc. Are you seeing this occur consistently?
More often than I would like, although the past couple of days not as much as before the weekend. Having a holiday in the US helps clear out scan backlogs, which is reducing the amount of errors that I am seeing.
If you have files that consistently produce this error (i.e. - copy "file X" into LDSCAN -- it produces that error), you may want to raise a support ticket. Just to clarify whether this is something "on us" or whether there's something bizarre in the inventory scan files themselves.
Usually "weird ass" issues like this I've seen being caused due to non-printable characters in the weirdest places. Oddly enough, the "non-printable character corruption" shenanigans is usually something I've seen more often originating on UNIX/LINUX systems than Windows ... go figure. But anyway - if there's "weird stuff" in the scan file, that CAN indicate that the workstation it's originating from may be pooched / in need of a rebuild.
Worth keeping in mind as an option (especially when it's only "scans from the same devices" that keep producing this error).
Hope that helps a bit.