According to the AP, Joker Al Franken's campaign tried to add votes to their tally that had already been disqualified. Fortunately, the Hennepin County Board of Elections shot them down. From the AP:
Minnesota's largest county has declined a request from Al Franken's Senate campaign to reconsider some disqualified absentee ballots. [...] Board members said the ballots could be dealt with during the upcoming recount.
These "votes" were from people whose signatures didn't match or who were not registered or improperly registered.
Norm Coleman's campaign issued a statement that cuts to the heart of the matter:
“The Al Franken campaign today tried to stuff new ballots into the ballot box in a brazen, last minute act of desperation. We have raised concerns repeatedly about these types of tactics by the Franken campaign. Today is further evidence of their intent to use whatever means necessary to counter the decision of the people of Minnesota. We applaud the actions of the Hennepin County Canvassing Board in rejecting this blatant, desperate act.”
The "desperation" point is key. The Franken campaign is running out of ways to steal the election. So they are flailing for lame mechanisms to do so.
They are afraid.