seawasp | Strange Thunderbird behavior... (Reply)

I use Thunderbird for my News client. Lately it's taken to popping up a box while I'm in the middle of reading news, and the box is mostly unreadable, apparently because the text is white and the background is white. I think I managed to read some lines that said "life of a mail client survey"? And had checkboxes, and a button for "submit". I've been closing it with the typical "X" icon in the corner, but I really have no idea what the heck's going on.

(note: this is on a Mac, not a PC, so anything having to do with Windows, etc., wouldn't apply)