A client was having a problem uploading documents to a SharePoint 2010 library last week. After filling out the Upload Document pop-up dialog box they got a basic browser “An error has occurred” message.
Message: Unexpected call to method or property access.
I found a KB article (979887) that mentions this error message and indicates that the problem is fixed in the latest security updates for Internet Explorer 8 (MS10-018 at the time of writing).
The client used the Microsoft Windows Update site (http://www.update.microsoft.com) to apply the updates and the problem vanished.