problem with upgrade from 10.04 to 10.10

[wufei34]

hi everyone am try to upgrade my ubuntu 10.4 LTS to ubuntu 10.10 and when i follow the procedure in
https://help.ubuntu.com/community/MaverickUpgrades
this error appear in the update manger :

W: GPG error: http://ppa.launchpad.net karmic Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 638ABCA0FA3A1271
W: GPG error: http://ppa.launchpad.net intrepid Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 638ABCA0FA3A1271


so if anybody can help me to know what is the problem exactly and tell me how i can upgrade to 10.10

thxx soo much

[mörgæs]

It seems like you have some cruft from 9.10 on your system. You could try to disable all PPA's or go for a clean install, if that does not help:

http://www.ubuntuforums.org/showthread.php?t=1580857