When I click "email PDF" on the sales invoice I receive an error message:

SIN003349 - SendEmail failed. First exception on row 0; first error: STRING_TOO_LONG, Content Type: data value too large: application/pdf; name="=?ISO-8859-1?B?QlNIIEV2IEFsZXRsZXJpIFNhbmF5aSB2ZSBUaWM=?= =?ISO-8859-1?B?YXJldCBBLj8uIEludm9pY2VTSU4wMDMzNDkucGRm?=" (max length=120): [ContentType]

I'm going through the Site.com Workbook, trying to add a datatable to a site.com site, but the only data available from a custom object are the standard fields.  I have edited the guest user profile via the site configuration link in the Overview tab of the site to enable read access to the custom object.  I can not find where to set field-level security on the custom object because the guest user profile is not included in the list of available profiles for the objects FLS.