ssl-exit-error

I have many log entries in the event log stating ssl-exit-error. all come from different external source IPs. In the Fortinet documentation it states: Message ID 99841 Log Type Event Log – SSL VPN session Severity Error FortiOS version 4.0 Messages action=exit ui=<remote_ip> msg=“SSL Exit Error: from <remote_ip> <state_of_SSL_connection>” Meaning An error occurred in the SSL connection. But what does this mean in detail, what produces this type of error message? cheers