The String Too Long Error is from Quickbooks telling us that a CUSTOMER or CARRIER name is longer than the 42 character limit.
First, find the first BLUE/Purple colored line in the export screen.
This is the FIRST record that failed and the one that needs attention.
1) Make note of the customer/carrier name
2) Go to dispatch and to the proper tab (customer or carrier)
3) Find the one in question
4) Alter the BILL TO/ PAY TO name (not the PHYSICAL address) to a length shorter then 42 characters.
5) Click the SAVE button (looks like a floppy disk) or move to another record to force a save.
6) Go back to export screen and try again.
NOTE: You may have to REVERSE the invoice and re-process it to get the new, shortened, name to export.
Please review this article that explains character limits in QuickBooks: