Has this been answered? We face the same issue. The users run into this intermittently. I cannot duplicate it. I have always been able to activate every BOM that they cannot. I have another system administrator who has the problem intermittently as well so it is not the role. I have tried clearing usage data and clearing the cache files on the local machine and it didn't resolve it.
There hasn't been any activity on this post for 6 months so I'm wondering if it just stopped happening rather than getting resolved.
