I recently had to install Office 2010 64bit on my computer to work with some extremely large Excel spreadsheets. I noticed today that when I tried to open one of the SharePoint list in datasheet view, it came up with the following error:
The list cannot be displayed in Datasheet view for one or more of the following reasons: A datasheet component compatible with Windows SharePoint Services is not installed, your browser does not support ActiveX controls, or support for ActiveX controls is disabled
This is a known compatibility issue between Office 2010 64bit and SharePoint. Microsoft has a workaround for this issue.
Install KB2266203 from Microsoft.
After installing the fix, the problem was resolved immediately.