Hae, oder was will aptitude?

Eben auf dem Server (Lenny):

Hole:2 http://security.debian.org lenny/updates Release [40,8kB]
Ign http://security.debian.org lenny/updates Release       
Ign http://security.debian.org lenny/updates/main Packages/DiffIndex
Ign http://security.debian.org lenny/updates/non-free Packages/DiffIndex
Ign http://security.debian.org lenny/updates/contrib Packages/DiffIndex    
Ign http://security.debian.org lenny/updates/main Sources/DiffIndex        
Ign http://security.debian.org lenny/updates/non-free Sources/DiffIndex    
Ign http://security.debian.org lenny/updates/contrib Sources/DiffIndex     
Treffer http://security.debian.org lenny/updates/main Packages             
Treffer http://ftp-stud.fht-esslingen.de lenny/non-free Packages/DiffIndex 
Treffer http://ftp-stud.fht-esslingen.de lenny/contrib Packages/DiffIndex  
Treffer http://ftp-stud.fht-esslingen.de lenny/main Sources/DiffIndex
Treffer http://ftp-stud.fht-esslingen.de lenny/non-free Sources/DiffIndex
Treffer http://ftp-stud.fht-esslingen.de lenny/contrib Sources/DiffIndex
Treffer http://security.debian.org lenny/updates/non-free Packages
Treffer http://security.debian.org lenny/updates/contrib Packages
Treffer http://security.debian.org lenny/updates/main Sources
Treffer http://security.debian.org lenny/updates/non-free Sources
Treffer http://security.debian.org lenny/updates/contrib Sources
Treffer http://ftp-stud.fht-esslingen.de lenny/non-free Sources
41,0kB wurden in 1s heruntergeladen (23,1kB/s)
Paketlisten werden gelesen... Fertig
W: GPG error: http://security.debian.org lenny/updates Release: Die folgenden Signaturen waren ungültig: BADSIG A70DAF536070D3A1 Debian Archive Automatic Signing Key (4.0/etch) 

Jo was iss denn das nu?
Denke mir ich warte mal ab.