When the link to a monitoring port is lost, the port pair will disable itself by design.
This doesn't appear to be a feature in 6.0 according to that CLI guide, however in 6.1 and above If these ports are set up in a fail open configuration (either built-in or through an external passive FO kit) you can use the 'setfailopencfg restore-inline' sensor CLI command to allow the port to enable itself. More information about that command can be found on page 39 of the 6.1 CLI guide: https://kc.mcafee.com/corporate/index?page=content&id=PD23297
I'd also recommend upgrading from version 6.0 to at least 6.1, preferably 7.1 or above. 6.0 is at the end of life date, and 6.1 is approaching the EoL date of July 31st.