Import Will Not Import Custom Field Data

Import will not import custom field data.

Attached are screenshots of a field mapping including custom field data. The data is good data, properly formatted. If you want to see the .csv I will email it to you.

The error report provides no clues as to which field specifically generated the error, just says:

1 Invalid value for custom field ''
2 Invalid value for custom field ''
3 Invalid value for custom field ''
4 Invalid value for custom field ''
5 Invalid value for custom field ''
6 Invalid value for custom field ''
8 Invalid value for custom field ''
9 Invalid value for custom field ''
11 Invalid value for custom field ''
12 Invalid value for custom field ''
13 Invalid value for custom field ''
14 Invalid value for custom field ''
16 Invalid value for custom field ''
17 Invalid value for custom field ''
18 Invalid value for custom field ''
19 Invalid value for custom field ''
20 Invalid value for custom field ''
21 Invalid value for custom field ''
etc etc etc