Let’s say you just created a brand spanking new document library and you want to transfer a bunch of files all at once because it would really be a chore uploading them one at a time. Then, when you open the ‘Add Document’ dialog, you don’t see the familiar ‘Upload Multiple Files…’ link. Also, the ‘Upload Multiple Documents’ button in the ribbon will be disabled. Don’t panic it might be a very simple solution. First, ask others – see if you are the only one to which this happens.
There are other possibilities, but for me, when it happened, I had been having problems with IE, so I uninstalled and re-installed. As it turns out the iexplore.exe file I was using was the 64 bit version, which apparently has a problem with a lot of Activex controls that SharePoint uses. You will probably have a problem with Excel Services if you are using this version. If this is the case, just revert back to using the 32 bit version and everything should work just fine. The 32 bit version will be in the Internet Explorer folder in the Programs (x86) folder. The 64 bit version is in the ‘Programs\Internet Explorer’ folder.
if you don’t know for sure which version you are using, just go to the ‘Help/About Internet Explorer’ menu item. On the ‘version’ line, if you don’t see ’64 bit’, then you’re OK. If you see it, you are definitely using the 64 bit version.
All Things DotNet Discussed – Winforms/ASP.Net/SharePoint/WPF