When Identity Manager is integrated with SiteMinder policy server, all password policies are enforced by the policy server. When the policy server returns an error message that is not expected by Identity Manager, IM interprets this as a corrupted buffer, as it is expecting a simple pass/fail message from the password policy instead.
To troubleshoot the problem when this error occurs, make a note of the timestamp for the error in the IM logs and find that same time in the associated policy server's smps.log. The error message in the smps.log will be the issue that you need to address in order to solve the corrupted buffer problem.
Typically, this will be a missing password policy, or a bad connection to the user directory that is being operated against. You may need to open an issue with SiteMinder support for further assistance.