RSView32 primary communication driver 'none loaded'

I have an RSView32 project where very occasionally the primary communications driver changes itself from AB_ETH1 to 'none loaded', stopping the project, changing it back and starting the project anf it fine ??

CB

See link below, some talk about a dated ver. of RSLinx. Maybe?

http://rockwellautomation.custhelp...._new_search=1&p_search_type=answers.search_nl