After a quick look around, here's what I think is happening:
The OPL-update script creates all of the tables in the database that it needs to store the metadata from the problems. The maximum size of each column of each table is hard-coded in the script.
The author column in the textbook table is set to a maximum of 63 characters, and some of the author tags in individual problems exceed this. I took a look at my database, and in my case it looks like it just truncates whatever doesn't fit. It would appear that your server is set up to spit an error if it can't fit the data into the field.
The quick fix should be to edit the OPL-update script and change line 203 from
author varchar (63) NOT NULL
author varchar (100) NOT NULL
This will allow up to 100 characters in the author field of that table. Hopefully this is the only offender for things that exceed the maximum space, and this allows OPL-update to complete.