Comment 16 for bug 908864

CUPS 1.5.0 has a new security policy for filters and backends not allowing group write permissions. See

http://www.cups.org/documentation.php/doc-1.5/whatsnew.html

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Scheduler

4. Filter security; Filters and backends must now have group write permissions disabled.
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So you will need to run

sudo chmod 755 /usr/local/lexmark/lxk08/bin/printdriver

for CUPS to accept the Lexmark driver in Oneiric.

Please also report this to Lexmark so that they update their driver to work with CUPS 1.5.0 and later.

Closing as this is a problem of a third-party driver.