This issue of libcoguador is something for which even Cognos does not provide a definitive answer because the reasons that cause this issue could be anything from your LD_LIBRARY_PATH, .profile, TNS Entries, oracle libraries, fully qualified domain names in TNS entries, etc etc.
According to my experience (may not be 100% solution), Cognos does not end the connections to database even after a report execution is completed. Too many connections from Cognos to your db could be the issue. Restarting your cognos server should solve it (but not a permanent solution). Restart closes all connections to database.
I am still researching, somewhere in cognos you can set the timeout for db connections. I have to try this option before I can suggest you.