Select the Gmail message content (or Ctrl+A to select the entire page) in Firefox, then copy/paste or drag/drop into UR, or copy (Ctrl+C) and then use the UR global import hotkey (default Win+V) to import into UR. Gmail does something funky with the page object model and the UR Firefox add-in can't retrieve the selected content like it can for most web pages (otherwise the Copy to UR button/menu could be used instead).
Other options:
1) Use basic HTML mode in GMail.
2) Use POP3 to download GMail using a client email program like Outlook Express, Windows Mail, Windows Live Mail, or Thunderbird, then import from that program into UR.
http://www.kinook.com/UltraRecall/Ma...pplication.htm
http://www.kinook.com/UltraRecall/Ma...ntegration.htm