What are you doing when that error occurs? Is it intermittent or reproducible? If reproducible, does it go away if you reboot your PC?
One thing I have found that can cause intermittent build errors is anti-virus checking in your build output folder. So, if this is a build error, and you have not disabled AV checking for your output folder, try that first.
Marjorie
My goal in life is to be as good a person as my dogs already think I am.
I wonder if it is truly only text that was pasted or if there are some tags or other items in there that mess up the structure. Try pasting the text first into Notepad and then from there copy it to the clipboard again and then paste into Contributor. That way any non-text portions will be stripped out.
If this is a common task and a common problem you run into then take a look at ArsClip. That is a clipboard manager application that can convert anything copied to the clipboard to plain text automatically.