When you copy text from a Rich Text box in Infopath on a computer that has IE7 installed, the pasted text unexpectedly appears inside a table cell
This issue occurs after you install Windows Internet Explorer 7 on a computer that has Infopath installed. Or, this issue occurs after you install InfoPath on a computer that is running Windows Vista.
To edit XML files, InfoPath uses the XML capabilities in Internet Explorer to perform certain functions, such as the copying-and-pasting of XML objects. Internet Explorer 7 handles copy-and-paste operations differently from pre-Internet Explorer 7 versions of the browser.
http://support.microsoft.com/default.aspx/kb/937053