What is the exact wording of the error?  I suspect there was in fact somebody logged in or a hung session with files open so the backup is incomplete.
 
How far did it get before the update failed?

According to the BTrieve documentation error 30 means:  
 
The file specified is not a microkernel file.
 
The status code is returned in the following situations:
 
1. The microkernel is not create the file
2. While using an earlier version of btrieve you opened a file created by a later version that has a format incompatible with the earlier version
3. The first page of the file may be damaged
4. You have attempted to access a valid file but your btrieve engine is older than the version that created the file (basically same thing as #2 above).
 
Thats basically what the btreive documents say. Now, if I had to guess why you are getting the error I'd guess that there is some sort of incompatibility with the btrieve engine and your files. Did the updater maybe convert your files to a newer format and you are still using an ancient version of btrieve? Your restore should have taken care of that unless 1. The files were locked because someone else was using them or 2. You didn't backup/restore ALL of the files and thus there is still a bad file somewhere. The first point in that sentence tends to cause the second point.