This is from the Seattle Times:

About 1,100 King County residents are not eligible to vote in the November election because a box containing their voter-registration forms was sent by UPS rather than U.S. mail, election officials said Friday.

The signed forms, collected in Pierce County during a drive to register more minority and low-income voters, were picked up by UPS one day before the Oct. 7 deadline for mailing registration forms. They arrived at election headquarters Oct. 9.

Because state law allows registrations to be processed only if there is a “postal cancellation” by the deadline, officials say these registrations arrived too late.

“They didn’t have a U.S. postmark that was posted in time,” Deputy Prosecuting Attorney Janine Joly said.

Elections spokeswoman Bobbie Egan said there was nothing on the package that confirmed the claim by the organizers of the voter-registration drive that they mailed the box before Oct. 7. The only date on a UPS shipping tag was Oct. 9.

But the tag also showed a UPS tracking number. UPS records showed the package was initially picked up in Fife at 2:05 p.m. Oct. 6.

The voter-registration drive, funded by Project Vote, was conducted by Washington ACORN (Association of Community Organizations for Reform Now). Registration forms from Pierce County residents were hand-delivered to election officials there, said Michael Slater, director of Project Vote’s election administration program.
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We’ve written in the past about problems like these involving third-party efforts to register voters; we typically have little data on the extent to which administrative errors like these may disenfranchise voters.