Eu resolvo meu problema reinstalando o owncloud. Ao reinstalar, eu recebo alguns problemas, que resolveu criando novo arquivo php.ini na pasta de instalação:
# Magic Quotes is enabled. ownCloud requires that it is disabled to work properly.
magic_quotes_gpc = off
magic_quotes_runtime = off
magic_quotes_sybase = off
# PHP PDO module is not installed.
extension=pdo.so
extension=pdo_sqlite.so
extension=sqlite.so
extension=pdo_mysql.so