Is this Vista 64 bit? If so, have you tried running in 32 bit mode?
I don't think we have seen an "Adobe Approved" version of RoboHelp for Vista 64 bit to date.
It is a 32-bit operating system.
Have solved this one - notes are here for anyone with similar problem.
The hint of OLEACC.dll led me to try likely suspect processes - and de-activating PwdBank.exe was what restored Robohelp access. Further reading led to the Toshiba support website, where PwdBank was associated with problems in TrueSuite Access Manager. My current version was 220.127.116.11. I upgraded (uninstalled old, installed new) to the latest version (18.104.22.168) and the problem is no longer occurring.