I've switched to a 64-bit operating system, and now the Chartspace control can no longer be added to the Toolbox? It doesn't even show up as an "additional control," which is needed to add it to the Toolbox; however, OWC11 can be referenced and scene in the object browser...

Has anyone tried to use OWC11 in Excel 2007/2010 on a 64-bit operating system?
I've run into the same problem. From what I can gather, the OWC11.dll library is not compatible with 64 bit software. In my case, I'm trying to display an OWC spreadsheet object on a user form in VBA with MS Office. It works in 32 bit office, but not with 64 bit office.