Looks like the repository index has been updated but the files not provided:
Reading package lists... Done Building dependency tree Reading state information... Done Calculating upgrade... Done The following packages have been kept back: vim (8.0.0586-pk => 7.3.547-7+deb7u3) The following packages will be upgraded: linux-image-3.2.0-4-amd64 (3.2.86-1 => 3.2.88-1) linux-libc-dev (3.2.86-1 => 3.2.88-1) owncloud-files (9.1.5-1.1 => 10.0.0-1.1) 3 upgraded, 0 newly installed, 0 to remove and 1 not upgraded. Need to get 38.0 MB/62.4 MB of archives. After this operation, 14.5 MB of additional disk space will be used. Do you want to continue [Y/n]? Err http://download.owncloud.org/download/repositories/stable/Debian_7.0/ owncloud-files 10.0.0-1.1 404 Not Found [IP: 2a01:4f8:192:50d6::3 80] Failed to fetch http://download.owncloud.org/download/repositories/stable/Debian_7.0/./all/owncloud-files_10.0.0-1.1_all.deb 404 Not Found [IP: 2a01:4f8:192:50d6::3 80] E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?
No v10 files here.