The issue is that if you have a rich text field inside a layout table, if you copy text from that field and then paste it into another rich text field elsewhere on the form outside that layout table, the paste includes a table and the text instead of just the text.
The issue happens when you have Internet Explorer 7 (IE7) installed. It doesn't happen when earlier versions of IE are installed.
Microsoft recently posted a KB article on this nasty issue and there is a hotfix available.
http://support.microsoft.com/kb/937053
Shiraz Cupala / Microsoft InfoPath MVPQdabra® Software / Streamline data gathering to turn process into knowledge