Copying calendar items "operation failed an object could not be found"

Copying calendar items "operation failed an object could not be found"

I am trying to merge several years' worth of calendar items into a single new PST file for archiving, but when I try to copy many of my calendar items I get this error:
"Outlook cannot copy the items. The attempted operation failed. An object could not be found"

Using advice elsewhere I tried creating and using a new mail profile, but now Outlook just hangs when I try to open one of my existing PST files (the item pane just displays "loading...").

Can anyone advise re. why I might be getting this error when copying calendar items from one folder/PST file to another?

I'm running Outlook 2010 on Windows 7 64-bit in a home environment (using Gmail/POP3).

Check this MS website & see if that is any help for you.

"The attempted operation failed. An object cannot be found." - Microsoft Community

Yes when I referred to "advice elsewhere" that was exactly what I was referring to.