Hi, I've discovered that there is some unfortunate interaction of boost::interprocess and at least one antivirus product (ESET Nod32). The problem manifests on some installations, and the symptom is that an interprocess_exception with a native error code of 32 (ERROR_SHARING_VIOLATION) occurs when a named_semaphore (or other named objects) are opened (well, I've only seen it when opening, but depending on the AV product I guess it may happen when creating as well). Googling a bit on this I found http://support.microsoft.com/kb/316609, which suggests that AV products take exclusive locks on files just as a file is being opened, which sometimes upsets calls to CreateFile. What they suggest is doing retries when a sharing violation occurs. I'm not really saying that this is a boost.interprocess bug, but at least for me it would be handy if it was a little bit more tolerant towards AV products. I've managed (after quite a lot of hard work) to get a test environment where I can reproduce this quite easily, so I'm more than willing to help out with testing. Cheers Lars