That's what Roll Call is reporting (subscription required):

[Illinois Secretary of State Jesse] White’s signature approving the appointment came hours after the Illinois Supreme Court ruled that White’ signature of certification was not necessary for the governor’s appointee to be considered legally able to take office as Senator.

“I, Jesse White, Secretary of State of the State of Illinois, do hereby certify that the attached is a true and accurate document setting forth an appointment made by the Governor of the State of Illinois,” White wrote Friday on a document titled “Certificate.”

But here's the AP's take:

White still refuses to co-sign [Roland] Burris' appointment paperwork with Gov. Rod Blagojevich.

But his signature is on a certificate requested by Blagojevich's office Friday. The certificate says a copy of Blagojevich's Dec. 30 appointment letter is "a true and accurate copy of a document setting forth an appointment."

A White spokesman says the certificate just acknowledges the document was filed. A request for the certificate could have been made at any time.

Having heard a rumor that White had signed the certificate yesterday evening, we talked to a spokesperson for the secretary, who said that White's position had not changed.  So while he complied with the Blagojevich administration's request for this document, he is still refusing to sign the certificate of appointment itself.  And that's what appears to matter. Remember, Dick Durbin was very specific yesterday about the need for the signature to appear on the certificate:

DURBIN: In 1884, the United State Senate drew up rules relative to the filling of vacancies by election or appointment.  And the rules of the United States Senate are clear: whether by election or appointment, a certificate has to be given to the Senate which declares the date of the appointment or election, the name of the person, the date of the certification, and the name and the signature of both the governor of the state and the secretary of state, as well as the name of the state, obviously, affected by this appointment.

These basic six requirements have been in the Senate now for 125 years. There has never in the history of the Senate been a waiver of the requirement that the secretary of state's signature be part of the appointment process. Never.  No one's suggested it. 

At this point, we've clearly reached an impasse.

In short, I don't think White's separate "certificate" is going to pass muster with the Democratic leaders.  But considering the way things have swung back and forth over the past week, it's no use trying to predict how they'll react.

UPDATE (10:42 am): WBEZ has a copy of the White document, as well as this tidbit:

Senator Durbin is the assistant majority leader in the Senate. He says the move by Burris may be enough to satisfy the Senate, though he stresses Senate lawyers will have to review it.