Symptom:
The IPS mainApp stops responding to control transactions due to the _S_create exception generating the following log message:

mainApp[619] Syslog/F errSystemError threadStart catch(STL logic error) basic_string::_S_create

The mainApp thread that terminated is most likely the CT processor that runs several different processes.  The /var/log/messages may display failed authentications such as the following:

sensor auth.err pam_tally[619]: pam_tally: pam_get_uid; no such user isoadmin
sensor auth.alert unix_chkpwd[19109]: check pass; user unknown
sensor auth.notice cid-auth(pam_unix)[619]: authentication failure; logname= uid=50 euid=50 tty= ruser= rhost=
sensor auth.crit mainApp[619]: mainApp[619] Syslog/F errSystemError threadStart catch(STL logic error)

Conditions:
Able to ping the sensor and get SNMP traps, but cannot login to the sensor getting the following message:  

Cid/E Error: Cannot communicate with mainApp (getVersion), errorMsg: Error: getVersion : Control transaction cannot be completed at this time