Error in xml_ns.xml_document(x) : external pointer is not valid

Hi,
I get this error when I open RStudio and my worskspace is loaded.
I have read that corrupted .RData file could be the reason.
How to check which object (inside .RData file) is corrupted or causing this error during R opening ?
I saved my workspace again and loaded it, and error persists.
How to check apart from sifting through all history panel, which objects were added as last ?
Please do not advise like: "you should always start R with clean global environment", because I would like to resolve this.
regards,

I'm getting this error when I load a project. So, I hope you get an answer.

It makes then two of us. I am still looking for anwer to this.