You log on to MOS (My Oracle Support) at support.oracle.com and put the number in the brackets in the search box. You have support, right?
Also noticed bug 9182633, (another thing you can put in the search box), listed as not a bug, because it is auditing, slower in the new version. Which is another thing you can look at, turn off auditing and see if connections go faster. (Search AUDIT_TRAIL in the docs)
It does seem that a 2 minute timeout is exactly that caused by a DNS lookup timing out. Are you sure the server can resolve TNS and DNS names?