Here's the error from one of my users:
The list is displayed in Standard view. It 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 just started happening this week. Only for one user. No recent patches on the sharepoint server.
If you search this on the internet, you get tons of results but nothing simple. I went through this good article, http://www.sharepointblogs.com/wsspectacular/archive/2008/04/14/when-datasheets-go-bad.aspx but nothing worked. Frustrating....
Then a local IT guy asked me if I tried clearing the Internet Explorer cache. Tried it and it worked!!!
Lesson: Try clearing the IE cache first before trying all the other stuff. May save you alot of time.
Server environment: WSS 2.0, server 2003
Client environment: XP, Office 2003