Thanks for the suggestion, Patrick.
I tried creating new CSV files, by importing the data into Excel. Unfortunately the files still contained unknown errors, and would not load via the CSV import.
I ended up breaking the CSV files down into smaller files, to figure out whether the errors were widespread or specific to certain records. Turned out to be the latter. Once I was able to isolate the offending records within the CSV files, I noticed that many of the fields in these records were blank (intentionally blank on the cataloger's part). I simply deleted these blank fields/columns, and all loaded fine via CSV import. The error appeared to lie in those blank fields, though I do not understand why.
Thanks again for the suggestions!