2. It works for first connection and throws the same 12560 error for subsequent connection attempts.
I tried reinstalling Oracle but the problem doesn't go away. I even tried installing Oracle on three different machines. Do you have any ideas? I am stuck badly and can't work anymore due to this issue.
This sounds like either a resource issue, a configuration problem, or a bug. If you're using some non-English languages or non-default character set(s), this may be part of the problem. There was at least one bug related to an NLS issue that may be related to your problem report, but it was too vague to tell for sure.
I'd make sure you have the most recent patchset applied and if the problem still reproduces, then I'd file a TAR with Oracle Support to nail down the root cause of the problem.
This was first published in May 2004